One person was killed and at least 17 injured when a shooting broke out at an all-night arts festival in Trenton early Sunday.Published OnJune 17, 2018CreditImage by Paige Gross/NJ.com, via The Star-Ledger, via Associated Press

One person was killed and at least 17 people were shot early Sunday morning at a cherished all-night arts festival in Trenton in what may have been a neighborhood dispute unrelated to the event, the authorities said.

The person who was killed, a 33-year-old man, was believed to have been shot dead by the police and was one of multiple gunmen, according to the Mercer County prosecutor's office. Officials said a second gunman had been arrested, and that it was possible there were others.

The authorities do not have any reason to believe the festival was targeted or that the shooting was an act of terrorism, Casey DeBlasio, a spokeswoman for the prosecutor's office, said. She said the authorities were investigating a nearby carjacking in connection with the shooting and that multiple other motives were being considered.

Reed Gusciora, the mayor-elect, confirmed there had been unspecified threats of violence before the shooting. He referred specifically to a Facebook post and said the city had increased the number of police and fire department workers at the festival. He said an investigation would determine whether the police had responded appropriately to the threat.

For many Trenton residents, who have long endured entrenched issues with crime, poverty and drugs, the shooting was a blow to the city's revitalization as an arts hub. The 24-hour arts festival, Art All Night, was a centerpiece of that effort.

More than 25,000 people were projected to attend the festival, now in its 12th year. It was held at the Roebling Wire Works venue, once home to a factory that supplied wire cables for the Brooklyn and Golden Gate Bridges.

"Trenton has been making a comeback. Art All Night has been the cornerstone of that comeback," said Krystal Knapp, who was volunteering at the event when the shooting took place. "It's just devastating to everyone in the community."

Ms. Knapp, who runs the local news websites Planet Princeton and Planet Trenton, was counting attendees at the entrance to the building around 2:45 a.m. when she heard scuffling inside, then screaming, and finally gun shots.

Droves of the thousand or so attendees scrambled for the door of the long, narrow building, pushing Ms. Knapp to the ground and bruising and cutting her knees. Paintings and artwork were knocked off the walls. A woman pulled Ms. Knapp behind a car as another woman nearby was shot in the leg.

Ms. Knapp stayed behind the car as, 15 feet away, a gunman was shot and killed.

Ms. DeBlasio said four people, including a 13-year-old boy, were in critical condition. A total of 22 people were injured, including the 17 who were shot.

Kate Stier, a spokeswoman for Capital Health, which runs the hospital treating some of the victims, said the others who were injured had been trampled.

"It saddens me that a public attack such as this is what has brought major attention to our capital city on Father's Day," Mayor Eric Jackson said in a statement.

Gov. Phil Murphy arrived in Trenton on Sunday morning and spoke at Galilee Baptist Church about the need for stricter gun laws.

"It's yet another reminder of the senselessness of gun violence," he said.

Last week he signed a package of gun control bills into law that would, among other measures, require the seizure of firearms when a mental health professional determines someone poses a threat, and require background checks for private gun sales.

New Jersey was ranked by the Giffords Law Center to Prevent Gun Violence as second to California in having the country's most stringent gun restrictions. The center was named for Gabrielle Giffords, the former congresswoman who was gravely injured by gunfire in 2011.

Festival organizers said in a statement on Facebook they were "deeply saddened" and that rest of the festival would be canceled. It was set to end at 3 p.m. on Sunday. They did not respond to a request for comment.

"Our hearts ache and our eyes are blurry but our dedication and resolve to building a better Trenton through community, creativity and inspiration will never fade," the statement said. "We're still processing much of this and we don't have many answers at this time but please know that our staff, our volunteers, our artists and musicians all seem to be healthy and accounted for."

Nick Corasaniti, Annie Correal and Luis Ferré-Sadurni contributed reporting.