"'I'm the shooter. It's me. I am the shooter,'" Gentili described Mateen as saying. Gentili said Mateen also told him, "'I did it for ISIS. I did it for the Islamic State.
The wife of the gunman who killed 49 people at an Orlando gay nightclub could face criminal charges as early as Wednesday after a federal grand jury was convened to study possible wrongdoing by her, a law enforcement source said.
Omar Mateen's wife, Noor Salman, knew of his plans for what became the deadliest mass shooting in modern U.S. history, said the law enforcement source, who has been briefed on the matter.
U.S. Senator Angus King, a member of the Senate Intelligence Committee, which received a briefing on the investigation into Sunday's massacre, told CNN it appeared Salman had "some knowledge" of what was going on.
"She definitely is, I guess you would say, a person of interest right now and appears to be cooperating and can provide us with some important information," King said.
Salman was with Mateen when he cased possible targets in the past two months, including the Walt Disney World Resort in April, a shopping complex called Disney Springs and the Pulse nightclub in early June, CNN and NBC reported.
Mateen, a New York-born U.S. citizen of Afghan heritage, was shot dead by police after a three-hour rampage through the Pulse nightclub. The attack was the deadliest on U.S. soil since the hijacked plane attacks on New York and Washington on Sept. 11, 2001.
Orlando Mayor Buddy Dyer opened a family assistance center at a stadium on Wednesday to provide help to victims of the attack and their survivors. Autopsies had been completed on all 49 dead, and that about 20 bodies had been released to funeral homes, he told reporters.
Bodies could not be removed for hours after the shooting, he said, because authorities initially feared the shooter had booby trapped the club. Ultimately, no explosives were found.
"We know that it's been traumatic for everybody, and we do know that we need to provide a lot of support," Dyer said.
Federal investigators have said Mateen, who was 29 and worked as a security guard, was likely self-radicalized and there was no evidence he received any help or instructions from outside groups such as Islamic State.
Salman's mother, Ekbal Zahi Salman, lives in a middle-class neighborhood in Rodeo, California, about 25 miles (40 km) north of San Francisco. A neighbor said Noor Salman visited her mother only once after she married Mateen.
Noor Salman's mother "didn't like him very much. He didn't allow her (Noor) to come here," said neighbor Rajinder Chahal. He said he had spoken to Noor Salman's mother after the Orlando attack and she "was crying, weeping."
The shooting raised questions about how the United States should respond to the threat of violence from militant Islamists at home and abroad. The Federal Bureau of Investigation questioned Mateen in 2013 and 2014 for suspected ties to Islamist militants but concluded he did not pose a treat.
The shooting reverberated through the presidential election campaign. President Barack Obama slammed Republican candidate Donald Trump for reiterating his proposed ban on Muslims entering the United States, joining fellow Democrat Hillary Clinton in portraying Trump as unfit for the White House.
Trump criticized Obama for not using the phrase "radical Islam" to describe the threat from Islamist militants. Obama replied that using that label would not accomplish anything.
'I AM THE SHOOTER'
Mateen made multiple calls to 911 emergency services during his rampage, which he used to declare his allegiance to various Islamist militant groups, some of which are at odds with one another. He also called a local 24-hour cable news channel, News 13, the station revealed on its website on Wednesday.
Matthew Gentili, who was the producer on duty at the time, described the call in an interview with the station.
"'I'm the shooter. It's me. I am the shooter,'" Gentili described Mateen as saying. Gentili said Mateen also told him, "'I did it for ISIS. I did it for the Islamic State.'"
U.S. officials were investigating media reports that Mateen may have been gay but not openly so, and questioning whether that could have driven his attack, according to two people who have been briefed on the investigation and requested anonymity to discuss it.
Barbara Poma, the owner of the Pulse nightclub, speaking through a representative, denied reports Mateen had been a regular patron.
"Untrue and totally ridiculous," spokeswoman Sara Brady said in an email when asked about the reports.
Mateen's father also rejected the idea that his son had been gay.
Mateen's ex-wife, Sitora Yusufiy, said her ex-husband had facets of his life that he did not share with his family, such as drinking and going to nightclubs.
"He did have a different side to him that he could not open up to his father about," Yusufiy told CNN. "It doesn't surprise me that he might be gay."
She has previously said he was mentally unstable and beat her and that she fled their home after four months of marriage.
Orlando is one of the United States' most popular tourist destinations, with its theme parks helping to draw more than 60 million visitors a year. As the city mourned Sunday morning's attack, a huge search began for a 2-year-old boy who was dragged off by an alligator in a lagoon on Tuesday while visiting Walt Disney World with his family.