Law enforcement officials released new details about the decision on Sunday morning to storm the Pulse nightclub in Orlando, where 29-year-old Omar Mateen — armed with a rifle and a handgun, and possibly explosives — had opened fire on clubgoers before taking hostages.
Orlando Mayor Buddy Dyer said that 49 people were killed in what is the country's worst mass shooting incident, and that 48 of them had been identified. The gunmen was also killed, bringing the total death toll to 50. The mayor said 24 of the victims' next of kin had been identified.
President Barack Obama also said Monday morning that Mateen was apparently inspired by extremist information disseminated over the internet, but said there's no evidence he was directed by militants abroad or part of larger plot.
Orlando Police chief John Mina said he made the call to storm the club after Mateen made it clear that he was going to kill his hostages.
"There was a timeline given and we believed that there was imminent loss of life that we needed to prevent," Mina said. "It's a tough decision to make knowing that people's lives will be placed in danger by that, our officers' lives would be placed in danger."
The full sequence of events is also not yet clear, but officials say Mateen first arrived at the club at about 2:00am, and exchanged fire with an off-duty, uniformed Orlando police officer who was working security and was near the entrance to the club.
It's not clear if the officer is one of the 51 people wounded in the attack.
Mateen then entered the dance floor area and used an AR-15-style assault rifle and a pistol to open fire inside the crowded, dark club, where last call had passed but loud music still pumped from the speakers. Witnesses reported confusion amid the initial burst of fire, which they said consisted of between 20 and 30 shots.
Mina gave the impression that first responders began to arrive and entered the club almost immediately, where they encountered Mateen still firing on clubgoers. Police engaged him in a gunbattle, and he then retreated to a bathroom in what turned out to be a three-hour standoff.
"At this time we were able to rescue dozens and dozens of people," Mina said of the officers' initial entrance into the club.
'We believed that there was imminent loss of life that we needed to prevent.'
Mina said there were two bathrooms involved in the standoff: One where Mateen was holed up with five or six hostages, and another bathroom where 15 to 20 people had taken refuge on the other side of the club. But he said it's not clear how many people managed to escape, or were killed, in either bathroom.
"After the initial victims were shot or he was in he was in one bathroom with we believe four or five hostages. there were people in the opposing bathroom about 15 to 20 people and unknown when we rescued dozens and dozens of people so we don't know which bathroom they came at this point, so that's all part of the investigation," Mina said.
Mina says it was during this time that police tried to negotiate with Mateen, who was "cool and calm."
The police chief said Mateen "didn't ask for much. We were doing most of the asking."
It was during this time that Mateen made a call to 911 call and pledged his allegiance to thge Islamic State and said he had explosives, Mina said.
Just before 5:00am, Mina said he made the call to breach the wall of the second restroom where other clubgoers had take shelter. People escaped from that room through the hole, then Mateen emerged and fired on police, who returned fire and killed him. The chief said police are investigating whether clubgoers may have accidentally been hit by the SWAT team's gunfire during the shootout.
By 5:53am Orlando police announced that Mateen was dead.
Law enforcement officials were looking for clues as to whether anyone worked with Mateen on the attack, said Lee Bentley, a federal prosecutor in central Florida.
"There is an investigation of other persons, we are working as diligently as we can on that," Bentley told a news conference. "If anyone else was involved in this crime, they will be prosecuted."
Officials stressed their belief that there were no other attackers, and that there's no evidence of a furhter threat to the public.
The Islamic State reiterated on Monday its claim of responsibility for the attack. "One of the Caliphate's soldiers in America carried out a security invasion where he was able to enter a crusader gathering at a nightclub for homosexuals in Orlando," the group said in a broadcast on its Albayan Radio
Although the group claimed responsibility, this did not necessarily mean it directed the attack: There was nothing in the claim indicating coordination before the rampage between the gunman and Islamic State.
Reuters contributed to this report.