Here's a timeline of the deadliest mass shooting in U.S. history, with at least 50 dead and at least 53 wounded at Pulse nightclub in Orlando, Florida.
This timeline is based on information provided by Orlando Police Chief John Mina, Orlando Mayor Buddy Dyer, the FBI, and other law enforcement authorities.
Gunshots shatter the night
Sunday, 2:02 a.m. ET: Shooting erupts at Pulse, a gay nightclub in the heart of Orlando, as some 320 people enjoy the club's "Latin flavor" event.
An officer working extra duty in full uniform at the club responds. He and two officers nearby open fire on the shooter, and a gun battle ensues.
The shooter goes inside the club, where a hostage situation develops. Some 100 officers from the Orange County Sheriff's Office and the Orlando Police Department respond to the chaotic scene.
2:09 a.m. ET: Pulse posts an urgent message on Facebook: "Everyone get out of Pulse and keep running."
A tense standoff follows. Police say they had to wait three hours to access the situation, get armored vehicles on the scene and make sure they had enough personnel.
2:22 a.m. ET: Shooter calls 911 to pledge allegiance to ISIS. He also mentions the Boston Marathon bombers.
3:58 a.m. ET: A post on Orlando Police Department's official Twitter account says: "Shooting at Pulse Nightclub on S Orange. Multiple injuries. Stay away from area."
Shooting at Pulse Nightclub on S Orange. Multiple injuries. Stay away from area. pic.twitter.com/5Di2mc6XUY— Orlando Police (@OrlandoPolice) June 12, 2016
5 a.m. ET: Heavily armed SWAT team members use an armored vehicle to smash down a door at the club, clearing the way for some 30 people inside to flee to safety. SWAT officers confront the suspect in the doorway, shoot and kill him.
5:05 a.m. ET: Post on Orlando Police Department's Twitter account says loud noise near scene was a "controlled explosion."
5:53 a.m. ET: Twitter account of Orlando Police Department posts that shooter is dead.
Pulse Shooting: The shooter inside the club is dead.— Orlando Police (@OrlandoPolice) June 12, 2016
7:15 a.m. ET: Orlando Police Chief John Mina announces at a press conference that multiple people have died inside the club. He says the shooter was armed with an assault-type rifle and a handgun.
10:15 a.m. ET: Authorities identify the Orlando nightclub shooter as Omar Saddiqui Mateen, 29, of Fort Pierce, Florida. Orlando Mayor Buddy Dyer updates the death toll to 50, with 53 others wounded.
12:03 p.m. ET: Florida Gov. Rick Scott posts on Twitter: "This is an attack on our people. An attack on Orlando. An attack on Florida. An attack on America. An attack on all of us." He declares a state of emergency in Orange County.
This is an attack on our people. An attack on Orlando. An attack on Florida. An attack on America. An attack on all of us.— Rick Scott (@SenRickScott) June 12, 2016
1:00 p.m. ET: President Barack Obama addresses the attack from the White House, calling it an act of terror and an act of hate.
The shooter was a "person filled with hatred," Obama says. He also orders the American flag be lowered to half-staff at the White House and all other government buildings until sunset on June 16.
"In the face of hate and violence, we will love one another," Obama says. "We will not give in to fear or turn against each other, instead we will stand united as Americans to protect our people, to defend our nation, and take action against those who threaten us."