The first blow came without warning. Pelon felt a metal ring crush his right cheekbone. He crumbled to the concrete floor of the garage as a man began a slow count. Uno! A kick to the head. Dos! A punch to the nose. Tres! A knee to the groin. Pelon lost track as a half-dozen men pounded away. It was a cool night in November 2013, and Pelon thought it might be his last.

When the count reached 13, it was over. The group pulled back and cheered, "Welcome to the Mara!"

The assault was an initiation. After months of running with his assailants in and around Boston, Pelon was now an official member of what many consider to be the most dangerous gang in America: La Mara Salvatrucha, or MS-13. Like many new recruits, he was a Salvadoran immigrant who had fled his violent homeland for a better life in the United States.

But he was hardly a natural fit for the gang. At 36, he was more than twice the age of the average MS-13 homeboys, teenagers typically groomed—or intimidated—to join at local high schools. He also lacked the signature tattoos and unofficial MS-13 uniform: blue T-shirt, L.A. Dodgers baseball cap and Nike Cortez sneakers. He preferred collared golf shirts and linen shorts. Getting "jumped in" was never part of his plan. He was a drug dealer who had been paying the gang for protection as he moved cocaine and guns up and down the East Coast. For cover, Pelon drove a gypsy cab around Chelsea, Massachusetts, a city of 35,000 across the Mystic River from Boston. He quickly became the preferred driver of gang leaders. As MS-13 systematically killed its rivals in the 18th Street gang, he had driven members to bury bloody machetes—their weapon of choice—and reveled in their war stories. Now that he was a full-fledged homeboy, they expected more of the man they called "the doggie with the car."

As Pelon steadied himself in the garage that served as the clique's clubhouse, Casper, a local MS-13 leader, put his hand on the new member's shoulder. "It's time to look for and kill chavalas," he said, using street slang for "punk."

There was just one problem: Though his new friends didn't know it, Pelon was already working with a rival crew—a task force of federal, state and local law enforcement officials dedicated to dismantling MS-13.

Kill, Rape, Control

Since taking office, President Donald Trump has often used MS-13 as political shorthand for immigrant crime, a justification for hard-line immigration policies. His administration argues that this "bloodthirsty" gang of "animals" represents "one of the gravest threats to American public safety." To be sure, it is not the largest gang in America (its members number around 10,000 nationwide), and despite the president's emphasis, analysts say it's far from a national threat; its activities are generally restricted to a few urban centers on the West and East coasts, and its victims are typically members of rival gangs. But for the communities where MS-13 operates, its brutality is infamous: teenagers cutting down teenagers with machetes.

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The gang was born in Los Angeles in the 1980s, when waves of refugees fled a civil war in El Salvador. Clashing with black and Hispanic street gangs in Southern California, they banded together to form their own organization. Over time, La Mara Salvatrucha became increasingly violent and moved east, establishing footholds in the suburbs of Washington, New York and Boston.

Unlike other gangs, MS-13 didn't exist purely to make money. Members sold guns and drugs, but life revolved around something else: territory. Specifically, the territory of its chief rival, another Salvadoran gang named Barrio 18, or 18th Street. The MS motto: "Mata, viola, controla," or "Kill, rape, control." To fund its expansion, it forced fellow undocumented immigrants—cab drivers, dishwashers and housekeepers—to pay protection money of $5 to $10 a week. Terrified of deportation, most coughed up instead of going to the police. Those who didn't often faced the end of a blade.

NW_MS13_INSTAmini Photo Illustration by Max-o-Matic for Newsweek

Mario Millet had never seen anything like MS-13. An undercover officer in the Massachusetts State Police, he had worked to take down a number of gangs since the 1990s, from the Hells Angels to the Latin Kings. But MS-13's ultraviolence shocked him, especially after members raped and battered two disabled teenagers in 2002. Both girls were deaf, and one was confined to a wheelchair with cerebral palsy. One of the girls' fathers, an 18th Street associate, had apparently "disrespected" the gang—and MS-13 had taken its revenge.

The crime became national news, and the FBI turned to its North Shore Gang Task Force, an elite squad of federal, state and local police serving Boston's northern suburbs. The work was hard, and progress was slow. Millet and many of his colleagues didn't speak Spanish, a disadvantage in the gang's base of Chelsea, where more than 65 percent of the population is Latino. Victims were reluctant to cooperate, fearing for not only their own lives but those of their relatives in El Salvador, where MS-13 controlled much of the country. The team's efforts resulted in sporadic arrests and some deportations, but the gang continued to kill.

Peter Levitt, the assistant U.S. attorney overseeing the task force, was frustrated. Typically, defendants facing charges are willing to serve as informants. "We needed to get someone into their network, to build their trust, and to take them down," he tells Newsweek. U.S. Immigration and Customs Enforcement (ICE) officials targeted MS-13 members facing deportation, hoping to flip them. It didn't work; the gang was too fearsome, too brutal. It was not uncommon for informants and their ­entire families, even infants and the elderly, to be chopped into pieces as retribution.

Then, in late 2012, years before Trump came into office, Millet received word from the FBI's top man in El Salvador: A local had approached him about MS-13, and he wanted to wear a wire. His street name: Pelon. His story—culled from court documents, audio transcripts, witness testimony and interviews with law enforcement—provides a harrowing glimpse into the murderous world of MS-13 and the high-stakes strategies the authorities have used to thwart it in Boston and along the East Coast.

FE_MS13_17_AP410206614667 MS-13 is notoriously violent and known for using machetes to kill victims. It's the only gang designated by the U.S. as a "transnational criminal organization." Charles Krupa/AP Photo

The Murder Capital of the World

On January 20, 2013, as President Barack Obama was sworn in for a second term, Millet and two of his colleagues flew to El Salvador. FBI Special Agent John Kelly was a Massachusetts native who had become an MS-13 expert while working gang cases in California. And Scott Conley, a Chelsea detective and former Green Beret, had been tracking the gang since the late 1990s. Officially, their cover was humanitarian aid; they were working for a nongovernmental organization, observing the dire conditions at El Salvador's prisons, where MS-13 leaders, or La Ranfla, ran the gang's international operations. In reality, they had arrived to vet their potential informant.

From 30,000 feet, the country looked like the perfect ­vacation destination: blue surf, green mountains, lush hillsides. But on the ground, it was entering its fifth year as the murder capital of the world. When a Salvadoran official picked them up at the San Salvador airport, he told them to keep quiet about their mission. Loose talk within earshot of a bellhop, cab driver, even uniformed police could make its way back to local MS-13 leaders.

That night, Conley and Millet went exploring after a party at the U.S. Embassy. As they sipped beers on a street corner, a van screeched to the curb, and its sliding door whipped open. Men in tactical gear and full face shields grabbed them by their shirts and yanked them inside. The men were FBI agents and scolded the two police officers for walking around in gang-controlled territory. "Are you fucking crazy?" one FBI agent shouted at them. "We'll be finding pieces of you all over the neighborhood."

The next morning, the three arrived at a hotel conference room: Millet in business attire and Conley and Kelly in board shorts and flip-flops. They thought the meeting was later and had just finished surfing. Pelon showed up in a janitor's uniform—a disguise FBI officials gave him so he wouldn't attract attention; the upscale hotel catered to diplomats. He stood 5-foot-11, with a muscled physique, save for a slight paunch. He grinned at the officers. "You went to the beach," he told Conley and Kelly, still wet from their morning workout. "I've never been to the beach in my country. Brave."

Like many Salvadorans, Pelon fled the country as a teen during the civil war in the 1980s, joining his brother in a trek north to Miami. For seven years, as an undocumented immigrant, he sold cocaine and guns for a Mexican drug cartel. He reveled in the Magic City's excesses, living in a luxury condo and racing sports cars around South Beach. At his peak, he had $5 million in real estate assets. Then, in early 2002, he got busted and was sentenced to 10 years in federal prison for drug trafficking. To shave time off his sentence, he fed the Drug Enforcement Administration information about associates in the cartel. The information led to new arrests, and the authorities reduced his jail time by three years.

To protect Pelon from retaliation, agents moved him from Florida to an immigration detention center in Massachusetts, where he awaited deportation to El Salvador. There, he quickly learned that his new cellmates were members of MS-13. He earned their trust by using the gang slang and dropping the names of drug dealers he knew from the "503," the area code for El Salvador. And since returning to his home country a few months earlier, he had kept in touch with many of his former cellmates.

FE_MS13_09 Muerto, the MS-13 member who introduced Pelon to the gang. Courtesy of U.S. Attorney's Office for the District of Massachusetts

Now, sitting before the police officers, Pelon ticked off a list of the homeboys he had heard about: Casper, Animal, Demente, Muerto, Smiley, Chucky, Roca, Little Crazy, Tigre, Lobo. He told the trio that he could help the feds convict them all if he went undercover. But he wanted something in return: a new life in the U.S. Returning to El Salvador, a country he hadn't seen in decades, had been a shock. He was living in a tin-roofed shack with family members.

"This is not a Third World country. This is a Fifth World country," he told them. "I want to get my whole family out of here. I want my sister's kids to have schools, learn English, get educations."

It was not the kind of arrangement the FBI would normally entertain. Bringing a convicted drug trafficker back into the U.S. as an undocumented immigrant is not easy. But as the task force knew after months of failed recruitment, no one had ever been willing to go undercover with MS-13.

For the next hour, Conley peppered Pelon with questions about Chelsea gang members who had been deported and risen in the ranks of La Ranfla. Millet studied his demeanor. After nearly two decades of talking to criminals, he knew liars. But Pelon seemed legit, more of a businessman than a bad guy, nervous but sincere.

Soon, the meeting wrapped, and the men stood up and shook hands. "I feel like I can trust you guys," Pelon told them. "You guys don't come across like feds." A Salvadoran military official working with the FBI then slipped Pelon out of the back of the hotel. The task force now had to convince ­Justice and Homeland Security officials that the risk was worth the potential reward.

The three lawmen went to the hotel bar. They ordered their beers and sat in silence for a while, until Kelly asked a question that was on all of their minds: "How the fuck are we going to pull this off?"

Millet kept another concern to himself: How the fuck are we going to keep this guy alive?

FE_MS13_07 Pelon drove a gypsy cab around Chelsea, Massachusetts, secretly recording gang members boasting about their crimes. Courtesy of U.S. Attorney's Office for the District of Massachusetts

Taxi Driver

A month later, in February, Pelon was back in the United States—and working for the government. Operation Mean Streets was on. Pelon was posing as an undocumented immigrant, and it took him less than 48 hours to find Mi Salvador, a Chelsea bar filled with Salvadorans—some selling fake papers that would help him get a Massachusetts ID. He checked in to a low-rent motel in a gang-riddled part of the city and reconnected with the MS-13 members he had met in ICE detention. After a few weeks, he noticed that some of the most notorious homeboys couldn't afford cars. Pelon met with his handlers, and together they devised a plan. He'd become a gypsy cab driver, and the feds could wire the car to record confessions. "Think about it," Pelon told them. "These chavalas love to talk. Let's drive around and let them."

To cement his bond with the gang, he would hire members to provide muscle as he moved drugs from Boston to New Hampshire—long rides where he could talk to MS-13 leaders about their crimes. The feds were impressed. FBI agents bought a used silver Toyota Camry with tinted windows and outfitted it with hidden cameras over the driver's seat. They installed a kill switch so they could stop the engine and surround the vehicle if things went sideways. They also gave Pelon a miniature recording device to hide in his clothing and two phones: one to record his conversations with MS-13 members, the other to talk to his handlers.

For two months, Pelon drove around Chelsea, dropping hints to anyone with MS-13 tattoos that he needed help with "a bit of business." He also sold a gun to a guy with gang ties, telling him he needed a protection detail. Then he had a breakthrough: Two men got into his cab. One took the passenger seat; gang ink covered his left arm. The other sat in the back; he was short and looked too old to be a gangbanger. The tattooed man turned and pulled down the neckline of his T-shirt: the scripted initials M and S filled his chest. "You're Pelon, right?" he asked. "Doggie, I heard you're looking for some people."

Pelon felt a surge of adrenaline. He turned toward his passenger to capture the conversation and flashed the MS-13 horns, the gang's hand sign. The man introduced himself as Muerto, a homeboy in a burgeoning clique called Eastside Loco Salvatrucha. His clubhouse was a garage owned by the man in the back seat, CheChe.

Like Pelon, Muerto had fled El Salvador for the U.S. as a child. He stayed with his uncle in Los Angeles and washed dishes to pay back the loan his family had taken out to cover the cost of his "coyote," the man who had smuggled him into the country. At 14, he was jumped into MS-13. After stabbing a number of rivals, he was deported back to El Salvador, where La Ranfla promoted him. Now, he was in Chelsea helping the gang expand, and he told Pelon that leaders in the 503 had vouched for him.

Pelon detailed the scheme: He would need security for a trip north to New Hampshire to deliver 5 kilos of cocaine. He and Muerto would take the Toyota, and CheChe would follow in another vehicle.

"We need two cars?" CheChe snapped.

"There's no problem with the front, but it's the back that I need a tail," Pelon said, trying to ease the tension. "So that in case the cops turn their lights on us, what you can do is burn some rubber or move away from them." Muerto and CheChe were silent. "I don't trust anyone else," Pelon said, offering them $500 each for their trouble. The gang members agreed.

A week later, the trio drove north, just as Pelon had planned. He picked up cocaine from an undercover FBI agent in a hotel parking lot just outside Boston and delivered the drugs to another agent in New Hampshire who posed as a buyer. Task force officers followed him along the way, and a SWAT team stood ready nearby in the event that Pelon blew his cover.

The trip took three hours. Pelon was poised and professional. He pointed out landmarks along the way, signaling his location to the task force officers listening to the wire. Muerto was chatty. A couple of months earlier, he and other members came across a group of 18th Street guys in a Chelsea park. Because he'd been wearing the usual MS-13 colors, they immediately knew who he was. "I flashed the MS, and I said, 'It's La Mara, you sons of bitches. What's up?'" Muerto said he chased one guy anHelp (Reference for usage, configuration, and modules.)d stabbed him with a military-style saber. Pelon praised him: "Cool, doggie." These types of cold confessions, captured on hidden camera, were exactly what the task force needed.

After the fake drug deal, Pelon met his handlers in the parking lot of his hotel, outside Chelsea. The officers plugged a laptop into the cab's camera and downloaded the video, a process that would be repeated dozens of times in different locations.

Pelon was in.

Drug Runs and Pupusas

Over the next two years, Pelon lived The La Mara lifestyle. He partied at "destroyer houses"—group homes shared by MS members—and curried favor with leaders' girlfriends by giving them fake luxury bags the FBI had seized in raids. Muerto became his best friend and, after several drug runs, vouched for him at CheChe's garage. The two saw each other every day, eating pupusas (stuffed corn cakes), talking trash about other MS-13 cliques and making drug runs.

Soon, Muerto brought in other clique leaders on the protection jobs. Afterward, they asked Pelon for his cell number so they could hail rides. Sometimes, the task force officers could protect him; other times, he was on his own. There simply wasn't enough manpower to watch him around the clock. "We had to trust him, and he had to trust us," says Errol Flynn, a special agent with the Department of Homeland Security. Once or twice a week, Pelon would meet his handlers in a parking lot, typically late at night, to discuss the intel he was gathering.

Because of the nature of the job, informants are often paranoid, driven by constant fear of being discovered. Pelon certainly felt that way. He never lived in one place too long, moving from cheap hotel to cheap hotel. He often called his handlers to ask about routine chores, like where he could get his hair cut or gripe about his FBI pay—about $1,000 a month. "I need a new washing machine," he groused to Millet when the one at his rent-by-the-week motel broke.

Seven years of living well in Miami had left him with a refined palate, and he complained when Conley would take him to chain restaurants, like the Border Grill. "This is shit with taco sauce on it," he said. He preferred the "good Dominican spots" that Millet frequented. What was most important for Pelon, however, was respect. And when he felt that he didn't get it, he would call Millet. "I need to see Mr. Peter," Pelon barked, referring to Levitt, the federal prosecutor. He'd ask Millet to take him to the U.S. attorney's office on the ninth floor of the federal courthouse in South Boston so he could air his complaints in late-night grievance sessions. His biggest concern: "When is my family getting here?"

One night in November 2013, Pelon and Muerto were driving to dinner when Muerto asked him to make a quick stop at the garage; he needed to drop off his weekly membership dues. Casper and the clique had other plans. When Pelon and Muerto arrived, the gang formed a circle and pushed Pelon into the center. "He's been hanging with the dudes," the leader told the group. "We gotta jump him in." Pelon braced himself. "Nah. Nah, doggie," he yelled. "I'm too old for that shit."

It was as much a surprise to Muerto as it was to Pelon. Typically, the honor is reserved for guys who have killed 18th Street rivals. But Pelon had become such a mainstay that Casper made an exception.

FE_MS13_10 A gang leader named Crazy. Courtesy of U.S. Attorney's Office for the District of Massachusetts

Snitches Get Stitches

The next morning, Pelon met up with Millet and Conley. A large welt bulged above his right eye, and his body was covered with bruises. He was embarrassed; he had just been beaten by a bunch of kids half his age.

But homeboy status gave Pelon a deeper level of access to the gang. He was now able to record members-only clique meetings, where MS-13 discussed, for example, collecting dues from members who held jobs as handymen or busboys in some of Boston's finest restaurants. That status also brought more pressure. He had a girlfriend, someone else who could suffer retribution if he was discovered. Every day, he was surrounded by self-described killers, like Chucky, a member of a teenage crew that had recently brawled with 18th Street outside a domestic violence shelter. A 38-year-old mother of three died in the crossfire.

The police officers were nervous. The FBI had given the informant leeway to commit certain crimes to maintain his cover; murder was not one of them. If Casper ordered Pelon to kill, the feds would have to pull the plug on the operation.

Just before Christmas in 2014, as he was settling into bed with his girlfriend, Pelon got a call from Crazy, the leader of another local clique. An MS-13 member named Vida Loca had been drinking at an illegal after-hours bar in a Chelsea apartment when an 18th Street rival put out a lit cigarette on his arm. Vida Loca called for backup, and members brought a gun, unleashing "a rapid fire of beans" that killed one and left another critically injured. Crazy needed Pelon to help the homeboy flee the state. "You want to go to New York to drop [him] off over there? What do you say?" Crazy asked, offering him $400. Pelon couldn't say no; Crazy had a quick temper. "Be careful right now when you go," Crazy told him, "so that the police don't stop you, man."

Pelon hung up and paced back and forth in his hotel room. He needed a way to alert the task force without blowing his cover. He called one of his handlers. "I'll take out my rear taillight," he said, "so you can follow me easy and pull me over for the broken light." Pelon then drove to an East Boston destroyer house, where he picked up Crazy, the gang leader's girlfriend and the killer who was about to go on the lam.

Millet was waiting on the Massachusetts Turnpike. When Pelon drove by, he flashed his blue dome lights. Once Pelon pulled over, Millet shined his flashlight into the car, his other hand on his gun holster. "You have a broken taillight," he said. Pelon protested: "We didn't do nothing, man." Millet then pulled out a "Be On the Lookout," or BOLO, sheet with Vida Loca's face on it. He asked everyone to step out of the vehicle and arrested the shooting suspect.

Crazy was livid—and suspicious. Pelon got back on the road, but the gang leader brandished his machete at his side. "Pull over, doggie," he said. Crazy then walked to the back of the car to inspect the taillight. It was out, like Millet had said.

Just six weeks later, Pelon made another enemy. He stopped at a Mexican restaurant and found Lobo, a fellow clique member, at the bar drinking. It was a violation of gang rules because being drunk in public could lead to fights with civilians, something the gang tries to avoid. After several tequila shots, Lobo snatched a gun from his waistband and pointed it at a group of strangers. "Anyone want some beans?" he yelled.

Pelon walked out and called the feds. Minutes later, when Lobo found three police officers waiting for him in the parking lot, he remembered seeing Pelon's phone call. He thought he might be a snitch, and told CheChe about his suspicion.

The two asked Casper for a "green light"—the gang's slang for permission—to kill Pelon. But luckily for the informant, Lobo was considered unreliable and prone to explosions of violence. Casper had ordered him to stay sober, and the incident in the restaurant was a clear transgression. The gang leader ordered the clique to give Lobo a 13-second beating.

But he didn't deny their request to kill Pelon. He just needed more evidence to justify putting a blade to his neck.

FE_MS13_13 Gang member Chucky. Courtesy of U.S. Attorney's Office for the District of Massachusetts

The Way of the Machete

Pelon knew the penalty for snitching. And he got a reminder in the spring of 2015, when two homeboys named Roca and Chucky got into his cab and started talking about a fellow member who "went to squeal to the cops." Who? Pelon asked. "Clacker," Roca said. "We'll grab his head. We'll cut it off, dude. So that way he won't talk."

Pelon's heart sank. Many of the gang members he met disgusted him; he called them "MS motherfuckers." But in Clacker, he saw a lost 15-year-old boy. A couple of years earlier, Clacker's mother had paid a coyote the family's life savings, $2,500, to smuggle him out of Honduras after 18th Street killed his older brother. Following a two-month trek through the desert, he was detained at the border and then sent to Massachusetts to live with the father he had never met.

Two weeks into his freshman year at Chelsea High School, he met Roca and Chucky, who showed him a slickly produced recruitment video that romanticized thug life the way the Islamic State militant group (ISIS) did jihad. A hip-hop song thumped in the background: "We come with knives and machetes to kill the enemy, and we are prepared to cut them from their neck down to their navel." Clacker joined MS-13 and was soon hunting a rival gang that had killed his brother and now teased him in the high school cafeteria.

"You guys are certain the son of a bitch snitched?" Pelon asked Roca and Chucky.

They said they were, but they were wrong. Clacker had bragged about being MS-13 to girls at school, info someone then passed to police. He hadn't snitched.

Pelon decided to play along with Roca and Chucky. "Fuck, I'm in this too," he told the gang members. "This man is going around snitching, bro. He could give them all of our names, doggie." After Roca and Chucky left the car, Pelon called Clacker. "Leave," he told the teenager. "You've been given a green light, for real."

It was a risky move. If it worked, he would save Clacker's life. If it failed, Pelon could be murdered. He met with his handlers and shared the audio of the plot to kill Clacker. The feds were wary, but they also saw an opportunity to flip the young gang member, who could give them even more inside information and corroborate Pelon's recordings.

That night, Conley and FBI Special Agent Jeff Wood visited Clacker's house. "Your friends are going to kill you," Wood told the teenager. But Clacker refused to cooperate. Wood turned to the boy's grandmother. "We warned him. If he wants our help, he needs to ask for it," the agent said.

Meanwhile, to maintain his cover, Pelon persuaded Roca and Chucky to use him as the driver for the hit. The same night, Pelon circled the boy's house with the two homeboys and a hitman named Villano whom MS-13 had dispatched from New Jersey. Pelon listened as the assassin explained with clinical detachment how he intended to kill Clacker: "Nice and easy, just like with a hen when you search under the feathers so that you feel the pulse like that. You feel the son of a bitch like that until you feel the vein, and that's where you jab the knife in."

Chucky pumped his fist in the air from the backseat and pulled out a machete as the car pulled up to the house.

But Clacker was gone.

FE_MS13_02_569159859 MS-13 and its rival 18th Street are known to welcome new members with a "jump-in" ceremony. Here, members of the 18th Street gang initiate a member in an alley in Santa Ana, California. Aurelio Jose Barrera/Los Angeles Times/Getty

Catfishing the Enemy

Clacker's father had driven him to the U.S. Attorney's Office in South Boston to cut a deal. In return for his cooperation, the FBI would put the teenager and his family—including his mother in Honduras—into witness protection. But, a few months later, as Clacker outlined for federal prosecutors a series of MS-13 robberies, he dropped a name that no one was expecting: Pelon.

When he wasn't serving as the bureau's inside man, the driver had been helping MS-13 members rob fellow gypsy cabs. He served as a getaway driver on the heists and took a share of the profits. It was a clear violation of his deal with the bureau, and it put prosecutors in an awkward position. If they pressed charges, Pelon would be ineligible for witness protection if he eventually testified against the gang. If they let him off, it could harm the credibility of the FBI, an agency still smarting from public revelations about its unholy alliance with legendary Boston mobster Whitey Bulger, who committed 19 murders while working for the bureau.

Back at the MS-13 clubhouse, Clacker's disappearance fueled paranoia. Casper was already making members turn in their cellphones at the start of each meeting and patting them down for wires before they entered the garage. Pelon feared for his safety. And he had noticed Muerto looking at him suspiciously. Recently, they were driving in the cab when Muerto got a call from a fellow clique that needed backup in an 18th Street brawl. They raced to the scene. Wielding a knife, Muerto bolted after a rival and stabbed him repeatedly while he tried to escape under a car. But Pelon froze. "I didn't even know what was happening, dude," he told Muerto afterward. "I even got scared. I didn't know who to turn around and look for—if it was you guys, if it was the enemy or the friend."

That winter, the Salvadoran gang leaders, called La Ranfla, organized a national meeting of MS-13 in Richmond, Virginia. Demente, a top gang official, needed a ride. Pelon was wary of driving him: Demente had recently ordered the killing of a 15-year-old boy who had refused to join the gang. The boy was tricked into going to a beach, where he was stabbed to death.

Now, as Pelon headed south on I-95, Demente spent long stretches of time just staring at him. Pelon wondered if there was any meeting at all. Casper had been studying him more intensely, too. Lobo had stopped speaking to him. And CheChe had dropped the drug protection runs altogether. When they finally pulled up to a northern Richmond home, Pelon was convinced they were going to kill him. But inside, there were indeed leaders from California, Texas, Ohio, Arizona, Virginia and Maryland, the largest assembly of MS-13 leadership in U.S. history. Appearing via WhatsApp from his El Salvador jail cell was a La Ranfla leader known as Sugar. Demente asked Pelon to speak for his clique, the Eastside Locos.

The first order of business was, ominously, snitches. "You must be very careful about who you bring in and talk to," Sugar told the group. "The FBI gives them a car, gives them money, gives them everything, and when they give them all that, they loosen their tongues, you know." Another leader called for Clacker's execution: "The Mara makes him; the Mara removes him."

Pelon's chest tightened. Sweat soaked his T-shirt, which is where he hid a tiny recording device. Leaders moved on to other issues, but he stopped processing the information, staring blankly into the distance. He wondered if the task force officers were listening to his wire. Would his handlers save him from the blade? And then, he heard his name.

"What's happening, Pelon?" Sugar shouted. This was it, he worried. They knew.

But to his relief, the leader wanted his thoughts on a different problem: errant cliques that refused to pay dues to the gang's deportation fund, which MS-13 uses to bring homeboys back into the U.S. Casper had balked at paying. Seeing an opening, Pelon said he was willing to take over the clique. One leader had another idea: "Why don't you kill Casper?"

Pelon knew his days as an informant were numbered.

FE_MS13_11_458329272 Tens of thousands of families and unaccompanied minors have fled violence in Central America, only to join MS-13 in the U.S. Above, a boy from Honduras watches a movie at a McAllen, Texas, detention facility, which the U.S. Border Patrol opened to temporarily house children. John Moore/Getty

The Worst of the Worst

A month and a half later, just before dawn on January 29, 2016, roughly 500 police officers swept through the Boston area. Operation Mean Streets had reached its peak, and after the meeting in Virginia, the feds decided to pull Pelon out. "It was always on our minds as he was driving around with these known killers who live to kill informants: Do they know? Is this a setup?" says Flynn, the Homeland Security agent.

Fifty-six people were arrested that day, including Chucky and Demente, largely because Pelon had captured their confessions in his cab. At one site in East Boston, neighbors applauded as agents led an MS-13 member into a police cruiser in handcuffs. "These were the immigrants who we were protecting, the ones that were being victimized by the immigrants who preyed on them," Flynn recalled. As Conley put it, "We got the worst of the worst that morning." The number of defendants would swell to 61 as some of those who were indicted—including Muerto, the man who introduced Pelon to MS-13—began to cut deals with prosecutors. They agreed to testify against La Mara Salvatrucha in return for lighter sentences or to avoid deportation.

As a result of Pelon's undercover work in Virginia, the investigation reached well beyond the Boston area, ensnaring the head of MS-13's East Coast division, as well as Sugar, who was indicted, again, from his El Salvador cell. "He was the best informant I ever had," said Levitt, the assistant U.S. attorney, who's now in private practice. Over the past two years, all but one defendant either pleaded guilty or were convicted and sentenced to decades behind bars, followed by deportation. The final defendant is now on trial. The cases included six murders (three of the victims were teenage boys and one a young woman), 22 attempted murders and dozens of other violent crimes.

The Obama-era operation was the largest takedown of MS-13 in U.S. history, and Attorney General Jeff Sessions traveled to Boston in September 2017 to personally congratulate law enforcement officials and deliver a message to remaining MS-13 members. "We're coming for you," Sessions said. "We will hunt you down. We will find you. We will bring you to justice."

However, experts say the reality is more complicated. Some local police chiefs argue that the Trump administration's aggressive immigration raids have made many undocumented immigrants—the targets of MS-13—less likely to report crimes and cooperate with police. Last year, the FBI noted a nationwide surge in MS-13 killings. Undocumented teens are still being groomed, and girls are now being recruited—something that's banned in El Salvador. In fact, the girlfriends of MS-13 homeboys convicted in Operation Mean Streets have taken over some local cliques.

For his part, Pelon is now in hiding. After the takedown, the FBI made good on its deal; it declined to prosecute him for the cab robberies because doing so would jeopardize his family's safety. A total of 17 people related to Pelon now receive witness protection. He still talks to Millet, Conley and a few of his other handlers, who provide updates on the case. They visited him and his girlfriend after the birth of their daughter. MS-13 recently put out a green light for her.