Crisis negotiators with the Orlando Police Department kept Mateen on the phone for about 30 minutes as they attempted to talk him down, according to information released by the FBI. Investigators did not release the transcripts of those conversations, however, a 50-second conversation between Mateen and a 911 dispatcher was detailed by officials.

Authorities initially declined to include the shooter's name and the name of the "person/group to whom he pledged allegiance" in the transcripts but later reversed the decision amid public backlash.

"Unfortunately, the unreleased portions of the transcript that named the terrorist organizations and leaders have caused an unnecessary distraction from the hard work that the FBI and our law enforcement partners have been doing to investigate this heinous crime," the U.S. Department of Justice said Monday in a statement.

"I'm in Orlando and I did the shootings," Mateen told a 911 operator, according to the transcript released by FBI investigators.

Orlando police first received a report of multiple shots fired at Pulse nightclub just after 2 a.m. on June 12. About 30 minutes later, Mateen called 911 from inside the club.

Authorities released the following transcript of that call:

Orlando police dispatch (OD): Emergency 911, this is being recorded.
Omar Mateen (OM): In the name of God the Merciful, the beneficent (in Arabic)
OD: What?
OM: Praise be to God, and prayers as well as peace be upon the prophet of God (in Arabic). I want to let you know, I'm in Orlando and I did the shootings.
OD: What's your name?
OM: My name is I pledge of allegiance to Abu Bakr al-Baghdadi of the Islamic State.
OD: Ok, What's your name?
OM: I pledge allegiance to Abu Bakr al-Baghdadi, may God protect him (in Arabic), on behalf of the Islamic State.
OD: Alright, where are you at?
OM: In Orlando.
OD: Where in Orlando?
(End of call.)

Over the next hour, Mateen had three conversations with crisis negotiators. The first lasted nine minutes, the second lasted 16 minutes and the final call lasted three minutes, according to the FBI.

"In these calls the shooter, who identified himself as an Islamic soldier, told the crisis negotiator that he was the person who pledged his allegiance to (omitted), and told the negotiator to tell America to stop bombing Syria and Iraq and that is why he was 'out here right now,'" investigators wrote in a news release. "When the crisis negotiator asked the shooter what he had done, the shooter stated 'No, you already know what I did.'"

Mateen told negotiators that a vehicle parked outside Pulse was filled with explosives and warned that he was going to "ignite it if they (police) try to do anything stupid." Later in the call, he said he had a vest like the kind they "used in France," referring to the coordinated attacks on Paris that killed 130 people in November 2015.

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"In the next few days, you're going to see more of this type of action going on," he told a negotiator before hanging up. Authorities were unable to get ahold of him again, according to the FBI.

Around 4:20 a.m., police pulled an air conditioning unit out from a Pulse dressing room window to allow victims to flee from the club.

"As victims were being rescued, they told (police that) the shooter said he was going to put four vests with bombs on victims within 15 minutes," according to the FBI.

Authorities searched Mateen's vehicle and Pulse, but found no evidence of a vest or an improvised explosive device in the area.

Just after 5 a.m., OPD SWAT and the Orange County Sheriff's Office's Hazardous Device Team breached a wall to gain entry to the area where Mateen was hiding. Around 5:14 a.m. a radio call went out of shots fired at Pulse. One minute later, officers reported that police had "engaged the suspect and the suspect was reported down," according to the FBI transcript.

"There were no reports of shots being fired inside Pulse between the initial exchange of gunfire between responding officers and (the) shooter and the time of the final breach," the FBI said, citing OPD radio communications. Orlando Police Chief John Mina said at a news conference Monday that during those three hours, officers were inside Pulse.

Investigators continued on Monday to delve into the motives behind Mateen's attack. Ron Hopper, FBI agent-in-charge for Orlando, said the investigation "will last months, and maybe years."

U.S. Attorney General Loretta Lynch on Sunday said the transcripts would not include Mateen's pledge of allegiance to ISIS.

"What we're not going to do is further this man's propaganda," she told NBC's "Meet the Press." "We're not going to hear him make his assertions of allegiance."

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