Music blared and more than 300 people danced and milled about Pulse nightclub early Sunday as Orlando police officer Adam Gruler, who was working a security detail, searched the area for a teenager who had gotten into the club with a fake ID.
He couldn't find the kid, so he headed back to the club's parking lot.
That's when the shots rang out.
It was just after 2 a.m. Sunday. Gruler ran toward the entrance after hearing the shots.
He was met by gunman Omar Mateen. Armed with a .223 caliber semiautomatic rifle and a 9mm semiautomatic pistol, Mateen started exchanging gunfire with the officer.
Gruler quickly realized he was outgunned and called for backup. Gruler retreated and Mateen ran further inside the club.
Lt. Scott Smith and Sgt. Jeffrey Backhaus arrived a couple minutes later and rushed into the club. There was another flurry of shots between them and Mateen, the Orlando Sentinel reports.