Partial transcripts of 911 calls made by the gunman who slaughtered 49 people at a gay nightclub in Florida were released by the Federal Bureau of Investigation (FBI) on Monday.
"It's been one week since the shooting. As you all know, this is a very thorough and comprehensive investigation of the largest mass shooting we've had, the most significant terrorist act since 9/11. No stone is being left unturned," US Attorney Lee Bentley said during a press conference held to announce the release of the transcripts.
During one of the calls Omar Mateen made from the Pulse nightclub in downtown Orlando, he threatened to blow up a car rigged with bombs and to strap hostages into explosive vests, according to the transcript.
"You people are gonna get it, and I'm gonna ignite it if they try to do anything stupid," Omar Mateen said.
No explosive vests or bombs were found in the nightclub or the suspect's car, however, the FBI said.
Mateen, a 29-year-old security guard, paused several times during the three-hour siege at the club to speak by phone with emergency dispatchers and police negotiators, as well as to post internet messages pledging allegiance to Islamist militant groups.
"He does not represent the religion of Islam but a perverted view, which based on what we know today was inspired by extremist killers. We currently have no evidence that he was directed by a foreign terrorist group, but was radicalised domestically," said Ron Hopper, a FBI assistant special agent in charge.
Mateen told an emergency dispatcher he was wearing an explosive vest like the kind they "used in France," apparently referring to the deadly assault in Paris last November by Islamic militants, according to the transcript.
As patrons fled the club, they told police outside that the shooter said he was going to put four vests with bombs on victims within 15 minutes, the FBI said in its statement.
Mateen is a New York-born US citizen and Florida resident of Afghan descent, who has been described by US officials as "self-radicalised" in his extremist sympathies.
The partial transcripts originally did not include a pledge of loyalty that Mateen made to Islamic State's leader. Hopper told a news conference near the nightclub that only partial transcripts were released so as not to "propagate their rhetoric, their violent rhetoric."
Later in the afternoon, the FBI changed course and released the excerpt without omissions.
US House Speaker Paul Ryan accused the Obama administration of censoring references to the Islamic State militant group and called for the full transcripts to be released.
Mateen identified himself as an "Islamic soldier," according to the FBI, and he told a negotiator to tell the United States to stop bombing Syria and Iraq.
The Joint Terrorism Taskforce has conducted more than 500 interviews about the massacre, Hopper said, and has processed 600 pieces of evidence.
Orlando Police Chief John Mina said the initial engagement by authorities caused the gunman to retreat and barricade himself in a bathroom with hostages. He said officers were inside the club saving victims during the three-hour standoff.
"During that time, our officers were intermittently in and out saving people, rescuing people from inside the club," Mina said, rejecting any criticism that police had failed to act quickly enough to end the siege.
Authorities have said preliminary evidence indicates Mateen was a mentally disturbed individual who acted alone and without direction from outside networks.
The massacre at Pulse, which also left 53 people wounded, led to national mourning and soul-searching over easy access to firearms and the vulnerability to hate crimes of people in the gay, lesbian, bisexual and transgender community.
The killings also triggered an effort to break a long-standing stalemate in Congress over gun control.
The Senate was set to vote on Monday on four competing measures - two from Democrats and two from Republicans - to expand background checks on gun buyers and curb gun sales for people on terrorism watch lists.