Rick Jervis and John Bacon

USA TODAY

ORLANDO — The gunman whose shooting spree at a packed nightclub left 49 people dead sounded "cool and calm" in negotiations with police before officers stormed the club in a brutal firefight that ended the siege, Orlando Police Chief John Mina said Monday.

Also on Monday, several regulars at the Pulse club said Omar Mateen had patronized the club before the attack. One recalled seeing the gunman drink at the bar and another said he had used a gay dating and chat app.

A federal law enforcement official told USA TODAY that investigators believe Omar Mateen was in the Orlando area for several days prior to the shooting, suggesting the gunman carefully considered the target.

The official, who is not authorized to comment publicly, said investigators are reviewing Mateen’s possible consideration of other iconic targets in the Orlando area, including Disney World. That review was ongoing and it was not immediately clear how seriously other locations were considered, the official said.

Mina and FBI Director James Comey provided more details about Mateen, saying he talked to 911 dispatchers three times in the hours before he was killed by police. Comey said Mateen's comments were contradictory as he claimed his attack was in support of the Islamic State. Mateen also had expressed support for al-Nusra and other rogue organizations that are bitter enemies of the Syrian-based militant group.

Comey said Mateen apparently had been radicalized, at least in part through online websites. But Comey reiterated comments made earlier by President Obama that Mateen did not appear to have been directed by the Islamic State or been a part of a larger conspiracy.

Comey said his agency investigated Mateen twice since 2013 but found insufficient evidence to charge the 29-year-old security guard with a crime. On one occasion, Comey said co-workers were concerned after Mateen told them he hoped police would raid his apartment and assault his family "so he could martyr himself."

Comey said Mateen admitted making some of the comments but said he was lashing out at co-workers who bullied him because of his Muslim background.

Mina also revealed more details about Mateen and efforts to stop the carnage wrought early Sunday at Pulse, a gay club that had been rocking with music and dancing on Latin Night.

The massacre began with a gunfight outside the club between Mateen and an extra-duty officer in full uniform, Mina said. Other officers arrived within minutes and continued shooting at Mateen as he fled into the club, retreating with hostages into a bathroom, the chief said.

Orlando shootings unfolded 'like a rolling thunder'

FBI: Orlando suspect U.S. citizen, vowed allegiance to Islamic State

"We were able to save and rescue dozens and dozens, get them out of there," Mina said. He said Mateen called 911, declaring his allegiance to the Islamic State but also talking about explosives.

"Our negotiators were talking to him and there were no shots at that time," Mina said. Police also were in contact with terrified people trapped in the club. Mateen didn’t make any demands, Mina said.

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

Mina said he made the decision to conduct the assault, and at around 5 a.m., a SWAT team detonated explosives at a wall. The wall didn’t completely breach so an armored vehicle was used to punch through. Dozens of clubgoers came running through the wall as did the shooter.

Police engaged in a shootout with Mateen, killing him. Mina said the investigation would include an effort to determine whether any victims were shot by police in the chaos of the final assault.

“Loss of life was imminent,” Mina said of the decision to storm the nightclub. “We all knew that was the right thing to do.”

The White House said President Obama would travel to Orlando on Thursday to pay respects to the victims "and to stand in solidarity with the community as they embark on their recovery."

The city on Monday released the names of the 11 officers who fired at the shooter, asking the public to respect their privacy.

ATF Agent Regina Lombardo said two weapons were recovered at the scene from the shooter and a third was found in his car. CNN reported that Mateen recently attempted to purchase military-grade body armor from a local story but was denied.

Islamic State radio on Monday called the U.S.-born gunman "one of the soldiers of the caliphate in America."

Paul Wysopal, special agent in charge of the FBI’s Tampa Division, said FBI headquarters had dispatched teams of “scene reconstructionists” to piece together what happened now that all the victims had been cleared from the property. Law enforcement agents from a variety of agencies – including FBI, ATF and local agencies – were investigating more than 100 leads in connection with the shooting, he said.

“Bad events like this bring the community together, as we saw after 9/11,” he said. “And that includes the law enforcement community.”

Orange County Sheriff Jerry Demmings echoed a sentiment expressed by many in Orlando.

"This is not a war zone ... this is a civilized society we're living in," he said. "Now this is about putting our community back together."

Mayor Buddy Dyer said 48 of the 49 victims have been identified. A GoFundMe page set up to support the victims had drawn donations of more than $2 million Monday afternoon.

“We will not be defined by the act of a cowardly hater,” he said. “We’ll be defined by how we respond as a community.”

All but a few families of victims had been notified by Monday afternoon. Twenty-nine people remain hospitalized Monday morning, five of them in "grave" condition, Orlando Health said. Six operations were scheduled for Monday.

Also on Monday, Ed Henson, owner of St. Lucie Shooting Center, confirmed that Mateen had legally purchased two guns there a week to 10 days before the shootings. "I'm sorry he picked my place," Henson said. "I wish he picked no place."

He added, "He's evil. We happened to be the gun store he picked. It's horrible."

Appearing on CNN, Sen. Dianne Feinstein, D-Calif., said the FBI was going through Mateen's cellphone and computer "and thus far has found nothing that relates him to any other kind of activity or communication.”

Feinstein said she didn't believe that there had been "any kind of intelligence failure connected with this. I think, in my mind, what it points out is the enormous unpredictability of exactly who is going to be stigmatized and moved to this kind of jihadism.”

Mass shooting creates chaos at Orlando nightclub

Obama addressed the victims and their families, saying "we feel enormous solidarity" with the loved ones and friends of the victims. He also stressed the need to curb the availability of guns.

"If we have self-radicalized individuals in this country, they are going to be very difficult, often times, to find ahead of time. And how easy it is for them to obtain weapons in some cases will make a difference," Obama said. "We make it very easy."

Contributing: Jeff Gallop and Kevin Johnson, USA TODAY Network