The wife of the Orlando gunman could face criminal charges if the FBI establishes that she knew in advance he was planning a deadly attack.

Noor Zahi Salman has reportedly told agents that she tried to talk husband Omar Mateen out of the raid on the Pulse nightclub that became the deadliest gun massacre in US history.

Peter King, chairman of the homeland security subcommittee on counterintelligence and terrorism, told MSNBC after a classified briefing on Tuesday: "If it's true that she did know that it was going to happen and she tried to talk him out of it, then it's possible criminal action against her, and again there might be more involvement by her, so all that has to be investigated."

The possibility that Mateen, 29, did not act alone but received support from other individuals or groups is now central to the FBI's inquiry, King added. "If there's anybody else that he was dealing with, anyone else he was talking with, anyone else who may have known about this, this is all where the investigation is going now."

Wielding an AR-15-style semiautomatic rifle and a handgun, Mateen opened fire at the club early on Sunday in a three-hour shooting rampage and hostage siege that ended with a SWAT team killing him. On Tuesday the last autopsy on the 49 victims was completed.

Vice-president Joe Biden, briefed at a national security meeting, said the FBI is "getting to the bottom of the tragedy" and it is "becoming clearer and more straightforward than a lot of us even thought".

After the same meeting, Barack Obama said there was no information to indicate that a foreign terrorist group directed the attack. "It is increasingly clear, however, that the killer took in extremist information and propaganda over the internet. He appears to have been an angry, disturbed, unstable young man who became radicalised."

NBC News reported that Mateen's wife attempted to talk him out of the plot, citing officials familiar with her comments to the FBI, and that she was with her husband when he bought ammunition and a holster. She told the FBI that she once drove him to Pulse because he wanted to scope it out.

Another official said the FBI has Mateen's phone and will try to use data from it to see if he had visited the club before, the Associated Press reported. Investigators have not ruled out charging anyone who may have had advance knowledge of the attack. It was also reported that Mateen browsed militant Islamist material on the internet for at least two years before the mass shooting.

FBI director James Comey has said the group is trying to determine whether Mateen had recently visited Disney World, one of the Orlando's celebrated theme parks, to consider it as a potential target.

Mourners pay their respects at a memorial for the shooting victims.

Mourners pay their respects at a memorial for the shooting victims. Photograph: Joe Raedle/Getty Images

Disney, which is donating $1m to an official fund for victims of the shooting, installed metal detectors last December but declined to comment on the Mateen case. A spokesperson said: "Unfortunately we've all been living in a world of uncertainty, and we have been increasing our security measures across our properties for some time, adding such visible safeguards as magnetometers, additional canine units, and law enforcement officers on site, as well as less visible systems that employ state-of-the-art security technologies."

Salman was Mateen's second wife. It is not clear when they married but the Associated Press reported that a 30 August 2013 property deed in Saint Lucie County identified them as a married couple. The couple had a three-year-old son.

Salman will be key to the ongoing probe as conflicting narratives emerge, including evidence he had been influenced by militant Islamist ideas and reports he might have struggled with his own sexual identity.

Related: FBI to investigate if Orlando gunman's sexuality was a motive in shooting

A survivor of the massacre, Patience Carter, suggested on Tuesday that Mateen had an overt political motive. Cowering in a bathroom, she heard him demand that Americans "stop bombing his country" and pledge allegiance to Islamic State, she said.

Carter, 20, who is African American, told reporters at Florida Hospital: "He even spoke to us directly in the bathroom. He said, 'Are there any black people in here?' I was too afraid to answer but there was an African American male in the stall, where the majority of my body was, who had answered and he said, 'Yes, there are about six or seven of us,' and the gunman responded back to him and said: 'You know, I don't have a problem with black people, this is about my country, you guys suffered enough.'"

The account chimed with previous FBI statements that Mateen had called the 911 emergency service and made reference to both Isis and the Tsarnaev brothers, who were responsible for the Boston bombings. Investigators have said Mateen was probably self-radicalised and there is no evidence that he received any instruction or aid from outside groups such as Isis.

Soon after the attack, Mateen's father indicated that his son had strong anti-gay feelings. He recounted an incident when his son became angry when he saw two men kissing in downtown Miami while out with his wife and young son.

Several media reports quoted men as saying they had seen Mateen at Pulse many times or that he had contacted them via gay dating apps such as Grindr and Jack'd. But Pulse denied that he had ever been a patron. "Untrue and totally ridiculous," spokeswoman Sara Brady said in an email to Reuters.

Mateen's ex-wife, Sitora Yusufiy, told CNN she did not know if he was gay but added: "Well, when we had gotten married, he confessed to me about his past that was recent at that time and that he very much enjoyed going to clubs and the nightlife and there was a lot of pictures of him."

"I feel like it's a side of him or a part of him that he lived but probably didn't want everybody to know about."

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Ex-wife of Florida gunman Omar Mateen says he was 'mentally unstable'

Asked by the Guardian about rumours his son was gay, Mateen's father Seddique Mateen said: "It's not true. Why, if he was gay, would he do this?"

Mateen, investigated twice by the FBI, was on the government's terrorist watch list for 10 months before being taken off.

Thirty-three people remain in hospital, including six in a critical condition. On Tuesday the first of the seriously injured to speak of their trauma was Angel Colon at the Orlando Regional Medical Center. "He's shooting everyone that's already dead on the floor, making sure they're dead," he said, speaking from a wheelchair. "I look over, and he shoots the girl next to me. And I'm just there laying down and I'm thinking 'I'm next, I'm dead.'

"So I don't know how, but by the glory of God, he shoots toward my head but it hits my hand, and then he shoots me again and it hits the side of my hip. I had no reaction. I was just prepared to just stay there laying down so he won't know that I'm alive."

Related: Orlando terror attack: shooter's father speaks about his son's 'horrible act'

The attending trauma surgeon on call that night, Dr Chadwick Smith, said: "It was singularly the worst day of my career and the best day of my career. And I think you can say that of pretty much every person standing up here."

The atrocity continued to reverberate in Washington DC. Obama, who will visit Orlando on Thursday, launched a blistering assault on Republican presumptive nominee Donald Trump over the candidate's anti-Muslim rhetoric, which the president described as dangerous and contrary to American values.

"Where does this stop? The Orlando killer, one of the San Bernardino killers, the Fort Hood killer, [they] were all US citizens. Are we going to start treating all Muslim Americans differently? … Putting them under surveillance?"

He also angrily hit back at Trump's criticism over his non-use of the term "radical Islam", saying of those fighting Isis: "They know full well who the enemy is. So do the intelligence and law enforcement officers who spend countless hours disrupting plots and protecting all Americans, including politicians who tweet and appear on cable news shows. They know who the nature of the enemy is.

"So there's no magic to the phrase 'radical Islam'. It's a political talking point; it's not a strategy."

The Democrats' presumptive nominee, Hillary Clinton, said Trump offered "bizarre rants" and "demonstrative lies" in his response to the Orlando massacre. "The terrorist who carried out this attack wasn't born in Afghanistan as Donald Trump said yesterday, he was born in Queens, New York, just like Donald was himself."