Attorney General Loretta Lynch is visiting Orlando to meet with prosecutors, first responders and families of the victims of the worst mass shooting in modern U.S. history.

The trip Tuesday comes as the Justice Department continues investigating the June 12 massacre at the Pulse nightclub, in which 49 people died and dozens were wounded. Federal investigators who have conducted hundreds of interviews haven't ruled out charges against others in connection with the shooting and say they're still trying to determine why Omar Mateen, who died in a gun battle with police, picked as his target a popular gay nightclub.

More clues emerged Monday when the FBI released a partial transcript of phone calls Mateen had with a 911 operator and police crisis negotiators once the shooting got underway. He identified himself as an Islamic soldier, demanded to a crisis negotiator that the U.S. "stop bombing" Syria and Iraq, warned of future violence in the coming days and at one point pledged allegiance to Abu Bakr al-Baghdadi, the leader of the Islamic State, the FBI said.

Despite his declarations, the FBI says it's found no evidence the attack was directed by a foreign terrorist organization. Mateen instead appears to have radicalized on his own through jihadist propaganda on the Internet, part of a population of Americans that law enforcement officials have repeatedly expressed concern about.

The statements to police, which one FBI official said were made in a "chilling, calm and deliberate manner" were similar to postings he apparently made to Facebook around the time of the shooting.

"I let you know, I'm in Orlando and I did the shootings," Mateen said in one call that came more than a half-hour after shots rang out, the FBI said.

Shortly after the call with a 911 operator, Mateen had three conversations with crisis negotiators in which he identified himself as an Islamic soldier and told a negotiator to tell America to stop bombing Syria and Iraq. He said that was why he was "out here right now," according to the excerpt.

Mateen's name and the groups and people to whom he pledged allegiance were initially omitted from the excerpt. But the Justice Department reversed course later Monday, providing a more complete transcript confirming Mateen pledged allegiance to al-Baghdadi. The Justice Department said in a statement it initially withheld the names so as not to give extremists "a publicity platform for hateful propaganda," but the omissions became an unnecessary distraction.

The shooting has fostered discussion about U.S. government efforts to identify and thwart individuals bent on violence — Mateen had been interviewed by the FBI three times since 2013 as part of two separate investigations and placed on a terror watch list — but also about whether stiffer gun control laws are needed. The Senate on Monday rejected proposals from both parties to keep extremists from acquiring guns, including one that was publicly supported by the Justice Department.

The release of the 911 calls does add to the public understanding of Mateen's motives. But Lynch, speaking on Sunday morning talk shows, said federal investigators are still unresolved as to what drove him to violence and to what extent he may also have been motivated by anti-gay hatred.

Besides meeting with first responders and victims, she's also scheduled to appear Tuesday alongside Lee Bentley, the United States attorney in Orlando overseeing the investigation into the shooting. Investigators have done hundreds of interviews, including with family members, and are working in particular to determine how much knowledge his wife had of the plot.

Lynch's meeting with first responders comes as Orlando police face continued questions about the response to the rampage.

On Monday, police Chief John Mina said that if any fire from responding officers hit victims at the club, gunman Mateen bears the responsibility. He wouldn't give further details but said: "Here's what I will tell you. Those killings are on the suspect, on the suspect alone in my mind." He stressed that the officers "acted heroically."

Mina acknowledged that questions have been raised by media outlets and the public about whether Orlando police waited too long after the start of the rampage at 2 a.m. to send in a SWAT team about 5 a.m.

He said an exchange of fire between police and Mateen shortly after 2 a.m. prompted the attacker to retreat into a bathroom and take hostages, shifting the incident from a shooting to a hostage-taking. Mina said there was no additional gunfire for about three hours until the SWAT team entered the building, although survivors have described at least some firing taking place inside one of the bathrooms.

Surviving hostage Patience Carter, in a live televised interview two days after the attacks, described the attacker firing when he entered the bathroom and more firing when the SWAT team burst into the building.

"I think there's this misconception that we didn't do anything for three hours," Mina said. "I'm trying to clarify: That's absolutely not true. Our officers were within the club within minutes, exchanging gunfire with the suspect, forced him to stop shooting and retreat into the bathroom."

"From there, we let our negotiator take over and try to negotiate this to a peaceful resolution in an effort to save lives while our SWAT team set up," Mina said.

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Alex Sanz in Orlando and Jack Gillum and Sadie Gurman in Washington contributed to this report.