(CNN) -- The flash of a muzzle interrupted the darkness of the theater and the pop of a gunshot sent the two dozen moviegoers scurrying in different directions.
A few seats away from the shooting sat a deputy who had come to the the Grove 16 theater complex in Wesley Chapel, Florida, to watch a movie on his day off.
Now Alan Hamilton was thrusting himself into the middle of chaos, moments after a fatal confrontation between two other moviegoers, not knowing whether he might be fired upon.
The shooter, identified by police as Curtis Reeves, had taken a seat with the gun in his lap. When Hamilton grabbed the barrel of the .380 pistol, the two scuffled for a few seconds before Reeves reportedly let go of the weapon.
There were about 25 people in the theater Monday. Two nurses hustled down to the scene to attend to the wounded.
Chad Oulson, who had been shot in the chest, was struggling for life and one of the nurses gave CPR. Another checked on spouse Nicole Oulson, who was shot in the hand.
It was about six minutes later that Pasco County deputy Sgt. Steve Greiner screeched his patrol car to a halt outside the theater, thinking he was about to get involved with an active shooter.
There was a a lot of traffic on the radio and the cops feared they were encountering a mass casualty event like the July 2012 shooting in Aurora, Colorado, where 12 people were killed and scores were wounded.
People streamed out of the movie theater complex, frantic and screaming.
Greiner and his colleagues took a couple of minutes to put together a small team.
Rumors were being thrown out by witnesses. Deputies were given three different descriptions of vehicles to look for. There were multiple descriptions of the shooter.
"All that information in that chaotic short period of time we were digesting," the 25-year veteran told reporters Tuesday afternoon. Some employees came up to them and said shooter was still in theater 10.
Greiner took a team in, still thinking they were about to encounter a gunman. Inside, they found Hamilton detaining Reeves and the nurse trying to save Chad Oulson. The patron died later at a hospital.
Hamilton, a deputy in nearby Sumter County, turned the gun over to Greiner. It was jammed and couldn't have fired another shot.
Other officers took care of the remaining moviegoers, calming them down and trying to figure out what they saw.
One of those people apparently was Mathew Reeves, son of the suspected shooter and an off-duty Tampa police officer. He arrived at the theater just after the shooting and wasn't considered a witness, officials said.
The theater was evacuated and remained closed Tuesday.