Orlando police punched holes in the side of a nightclub after hours of fruitless negotiations with the ISIS-linked terrorist who killed 49 people inside, freeing dozens of trapped clubgoers and luring the killer outside, authorities said Monday as a more detailed picture of the deadliest terror attack on American soil since 9/11 came into focus.

Omar Mateen was “cool and calm” as he killed 49 people and then took hostages in a bathroom at the gay nightclub Pulse, later pledging allegiance to the Islamic State terror group during a 911 call, officials said. The death toll had been announced as 50 on Sunday, though authorities clarified Monday that that figure included the shooter.

Investigators said 48 of the 49 victims had been identified, 24 next-of-kin had been notified and crews had finally removed the scores of dead from the bloody scene.

Mateen, armed with a handgun and long gun, began his deadly spree around 2 a.m., engaging in a gun battle with a uniformed off-duty officer working security at the club’s entrance before he started shooting club patrons, wounding 53 in addition to the dozens killed, Orlando Police Chief John Mina said. Additional officers quickly responded, forcing Mateen to retreat into a bathroom with about four or five hostages while authorities rescued “dozens of injured and non-injured” from the dance floor and lounge and bar area, Mina said.

In the bathroom for about three hours, Mateen called 911 to pledge his allegiance to ISIS and engaged in unproductive negotiations with police. Mateen claimed he had a bomb vest and explosives, Mina said, though authorities have not said either of those supposed ordinances was ever found.

During this time he also expressed solidarity with the Boston Marathon bombers and called those terrorists his "homeboys," officials said. Boston authorities have not found a credible link between Mateen and the Boston bombers.

“He was cool and calm when he was making those phone calls to us,” Mina said.

Negotiations were mostly one-sided as police tried to resolve the assault without further loss of life.

“He really wasn’t asking for a whole lot and we were doing most of the asking,” Mina said.

There were no shots fired during the time Mateen was in the bathroom, Mina said. However, at least one of the hostages, who had been texting his mother, was later discovered among the dead.

Authorities came to believe “further loss of life was imminent” around 5 a.m., prompting a rescue operation that involved an explosive breach of the bathroom wall. But the explosion did not penetrate the wall completely, so an armored SWAT vehicle known as a BearCat was used to puncture a three-foot wide hole in the wall, about two feet off the ground, Mina said.

Mateen came through that hole in the wall with guns in hand and began firing at officers, who shot and killed him.

Mina was asked if any of the dead or wounded may have been killed by friendly fire during the final chaotic gun battle.

“[Officers’] backdrop was a concrete wall and they were being fired upon,” Mina said. “But that’s all part of the investigation.”

Mateen had a third weapon in his car, though ATF officials did not say what it was and were still working on tracing it. The other weapons used in the attack were purchased legally by Mateen during the last week, authorities said Sunday.

Florida Gov. Rick Scott said he asked President Obama to declare a state of emergency for Florida early Monday morning. Scott had declared a state of emergency for Orange County on Sunday.

The FBI said it had already processed 100 leads and was working to preserve forensic evidence at Pulse with a shooting reconstruction team. U.S. Attorney Lee Bentley said he did not know if anyone else would be charged in connection with the incident, but said there was no reason to believe “anyone connected to the crime is placing the public in imminent danger at this time.”

Florida Attorney General Pam Biondi said 14 victims’ advocates had been mobilized and compensation counselors were available to families who may not be able to afford funeral expenses.