"The witness advised that Martin was scared because he was being followed through the complex by an unknown male and didn't know why. Martin attempted to run home but was followed by Zimmerman, who didn't want the person he falsely assumed was going to commit a crime to get away before the police arrived," it said.
The affidavit said that "when the police dispatcher realized Zimmerman was pursuing Martin, he instructed Zimmerman not to do that and that the responding officer would meet him. Zimmerman disregarded the police dispatcher and continued to follow Martin, who was trying to return to his home.
"Zimmerman confronted Martin and a struggle ensued. Witnesses heard people arguing and what sounded like a struggle."
Calls to 911 captured a voice crying for help; that voice belonged to Martin, according to his mother; the neighborhood watch volunteer's relatives have said the voice was Zimmerman's.
One of the responding officers reported seeing a wound on the back of Zimmerman's head, and surveillance video appeared to show an injury.
"Zimmerman shot Martin in the chest. When police arrived Zimmerman admitted shooting Martin. Officers recovered a gun from a holster inside Zimmerman's waistband."
O'Mara said Zimmerman, who will plead not guilty, is worried about getting a fair trial in Sanford.
While O'Mara said he does not share those concerns, he told CNN the case may need to be moved out of Seminole County to get a fair and impartial jury.
Asked Thursday why his client had followed Martin, O'Mara told CNN sister network HLN, "I know so little about the evidence."
O'Mara, who began representing Zimmerman just hours before he was charged Wednesday, said they had not yet discussed the facts of the case.
A member of the U.S. Civil Rights Commission, meanwhile, said Friday that he will ask the agency to investigate state "stand your ground" laws, such as Florida's, that allow people to use deadly force if they feel a reasonable threat of death or serious injury.
"The Trayvon Martin case has raised serious and disturbing questions over whether these statutes allow an unacceptable component of racial bias into our justice system," Commissioner Michael Yaki said. "Allegations that shooters like George Zimmerman may have 'profiled' their victims based on their race and that 'stand your ground laws' improperly protect race-motivated killings needs review."
He added that there is not enough information on the laws and how they have been implemented.