CNN  — 

Here’s a timeline of the deadliest mass shooting in U.S. history, when a gunman killed 49 people and wounded 53 in the early morning hours of June 12 at Pulse nightclub in Orlando. This timeline is based on information provided by Orlando police Chief John Mina, SWAT Captain Mark Canty, Mayor Buddy Dyer, first responder dispatch, witness accounts, the FBI and other law enforcement authorities.

Gunshots shatter the night

Sunday, 1:58 a.m. ET: Some 320 people are enjoying a “Latin flavor” event at Pulse, a gay nightclub in the heart of Orlando. Clubgoer Patience Carter hears gunshots in the center section of the club shortly after she and friends agree to contact Uber for a ride home. They rush into a bathroom.

Around 2:02 a.m. ET: An officer working extra duty in uniform at the club hears gunshots and engages the shooter. The officer feels he is outgunned, retreats from the club, and calls for assistance. Two SWAT officers in a nearby patrol car are among units that respond and a gunbattle ensues.

Other patrol officers rush into the club during the shootout to pull survivors out.

The shooter retreats and after exchanging gunfire with a SWAT lieutenant in a hallway he barricades himself and clubgoers in a bathroom.

Some 100 officers from the Orange County Sheriff’s Office and the Orlando Police Department respond to the chaotic scene over the next 45 minutes.

2:05 a.m. ET: Patience Carter says the shooter enters the bathroom and shoots several people hiding there. People scream and scramble as blood flies. Then the gunman stops shooting.

2:06-2:07 a.m. ET: Shooting victim Eddie Jamoldroy Justice texts his mother from a bathroom stall:

–Mommy I love you

–In club they shooting

–Trapp in bathroom

–Call police

Police say they receive communications from from clubgoers who say they are trapped inside the bathroom. This is when they say they knew there were hostages.

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 later say they had to wait three hours to assess the situation, get armored vehicles on the scene and make sure they had enough personnel.

Approximately 2:22 a.m. ET: Shooter talks to 911 dispatch three times. He calls and hangs up. He calls and talks briefly. The dispatcher calls back. During the calls, the shooter pledges allegiance to ISIS. He also mentions the Boston Marathon bombers and a Florida man who died as a suicide bomber for al Nusra Front in Syria. Patience Carter says he also told a 911 dispatcher he wanted America to stop bombing his country. She said he started speaking a foreign language, probably Arabic, when he ended the call.

Approximately 2:45 a.m. ET: Killer calls News 13 Orlando and speaks to producer Matt Gentili. Shooter takes responsibility for the attack and claims he did it for ISIS. At some point, he also posts on Facebook.

2:49-2:51 a.m. ET: Justice texts his mother again:

–He;s in the bathroom with us

–women’s bathroom is

–(mom) is the man in the bathroom wit u