On his way back into the gated suburban Orlando community after stepping out, Martin, wearing a hood, was spotted by Zimmerman.
Zimmerman described Martin as suspicious because he was wearing a hooded sweatshirt and walking slowly in the rain, police later told residents at a town hall.
A dispatcher told him to wait for a police cruiser, and not leave his vehicle.
But about a minute later, Zimmerman left his car wearing a red sweatshirt and pursued Martin on foot between two rows of townhouses, about 70 yards from where the teen was going.
Zimmerman's pursuit of Martin did not of itself constitute a crime, Lee said.
Witnesses told ABC News a fistfight broke out and, at one point, Zimmerman, who outweighed Martin by more than 100 pounds, was on the ground and that Martin was on
top.
Austin Brown, 13, was walking his dog during the time of the altercation and saw both men on the ground but separated.
Brown, along with several other residents, heard someone cry for help, just before hearing a gunshot. Police arrived 60 seconds later and the teen was quickly pronounced dead.
According to the police report, Zimmerman, who was armed with a handgun, was found bleeding from the nose and the back of the head, standing over Martin, who was unresponsive after being shot.
Trayvon Martin had no arrest record or disciplinary action for violence as a student in North Miami's Krop High School.