The wife of the gunman who killed 49 people at an Orlando, Florida, gay nightclub knew of his plans for the attack and could soon be charged in connection with the deadliest mass shooting in modern U.S. history, a law enforcement source said on Tuesday.

The source told Reuters that a federal grand jury had been convened and could charge Omar Mateen's wife, Noor Salman, as early as Wednesday.

"It appears she had some knowledge of what was going on," said U.S. Sen. Angus King, a member of the Senate Intelligence Committee, which received a briefing on the attack on Tuesday.

"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 told CNN.

Mateen, who was shot dead by police after a three-hour standoff at the Pulse club early on Sunday, called 911 during his rampage to profess allegiance to various militant Islamist groups.

Federal investigators have said he was likely self-radicalized and there was no evidence that he received any instruction or aid from outside groups such as Islamic State. Mateen, 29, was a U.S. citizen, born in New York of Afghan immigrant parents.

"He appears to have been an angry, disturbed, unstable young man who became radicalized," President Barack Obama told reporters after a meeting of the White House National Security Council., citing an FBI source, said prosecutors were seeking to charge Salman as an accessory to 49 counts of murder and 53 counts of attempted murder and failure to notify law enforcement about the pending attack and lying to federal agents.

NBC News said Salman told federal agents she tried to talk her husband out of carrying out the attack. But she also told the FBI she once drove him to the Pulse nightclub because he wanted to scope it out, the network said.


During his rampage, Mateen systematically made his way through the club shooting people who were already down, apparently to ensure they were dead, said Angel Colon, a wounded survivor.

"I look over and he shoots the girl next to me and I was just there laying down and thinking: 'I'm next, I'm dead,'" Colon said.

Mateen shot him twice more, one bullet apparently aimed for Colon's head striking his hand, and another hitting his hip, Colon recalled.

Mateen made calls to emergency 911 dispatchers from the club in which he pledged loyalty to the leader of Islamic State, Abu Bakr al-Baghdadi, whose organization controls parts of Iraq and Syria.

He also claimed solidarity in those calls with the ethnic Chechen brothers who carried out the deadly 2013 Boston Marathon bombing and with a Palestinian-American who became a suicide bomber in Syria for the al Qaeda offshoot known as the Nusra Front, authorities said.

One official familiar with the investigation, who spoke on condition of anonymity, said investigators were only beginning to delve into the contents of Mateen's cellphone and other electronic devices.

The source said investigators believe Mateen browsed militant Islamist material on the internet for two years or more before the Orlando shootings.