2:02 a.m.: An off-duty officer working at the nightclub responds to shots at the entrance and exchanges fire with Omar Mateen. Mateen goes inside.
2:04 a.m.: Additional Orlando Police Department officers arrive on the scene after receiving a call regarding multiple shots fired at the nightclub.
Mateen opens fire and patrons hide, duck and flee.
2:08 a.m.: Police officers enter the building and engage in a gun battle with Mateen, which they say forced him to retreat to the restrooms. Witnesses report he moved in and out of the restrooms during the standoff.
2:18 a.m.: Police and SWAT officers initiate a full call-out.
2:35 a.m.: Mateen makes a 911 calls and during the conversations, he says that he was doing this because he wanted America to stop bombing his country.
2:35 a.m.: Mateen talks for the first time to the OPD's Crisis Negotiation Team for approximately nine minutes.
2:39 a.m.: Mateen returns to the restroom.
3:03 a.m.: Second crisis negotiation call occurs and lasts approximately 16 minutes.
3:24 a.m.: Mateen talks to the OPD's Crisis Negotiation Team for the last time for about three minutes.
4:21 a.m.: Police officers pull an air conditioning unit out of a dressing room window for victims to evacuate.
4:29 a.m.: The rescued people said the shooter was going to put four vests with bombs on victims within 15 minutes, but a search of the shooter's vehicle on the scene and later inside the nightclub revealed no vest or improvised explosive devices.
5:02 a.m.: Witnesses hear explosions as police attempt to breach the building with an explosive charge and armored vehicle.
5:14 a.m.: Witnesses say Mateen shoots more people, and police radio communications confirm that shots were fired.
5:15 a.m.: Police break through the walls and kill Mateen as he emerges.