The teenager went out to get some Skittles and a can of ice tea. On his way back into the gated suburban Orlando community, Martin, wearing a hood, was spotted by Zimmerman, 26.
According to law enforcement sources who heard Zimmerman's call to a non-emergency police number, he told a dispatcher "these a..holes always get away."
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.
Lee said Zimmerman's pursuit of Martin did not of itself constitute a crime.
Witnesses told ABC News a fist fight 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.
An officer at the scene overheard Zimmerman saying, "I was yelling for someone to help me but no one would help me," the report said.
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Another officer corrected a witness after she told him that she heard the teen cry for help.
The officer told the witness, a long-time teacher, it was Zimmerman who cried for help, said the witness. ABC News has spoken to the teacher and she confirmed that the officer corrected her when she said she heard the teenager shout for help.