trayvon_martin_2.jpgSANFORD, Fla. _ The police chief of the agency investigating the shooting death of an unarmed teen by a neighborhood watch leader in central Florida says no arrest has been made because there is no evidence to dispute the shooter's claim of self-defense.

Sanford Police Chief Bill Lee said Monday that the investigation into the shooting death of 17-year-old Trayvon Martin was wrapping up and the case would be turned over to the State Attorney's Office on Tuesday.

Martin's family has criticized the police department for not arresting 28-year-old George Zimmerman, who admitted to the shooting but claimed he was defending himself.

A police report says Zimmerman initially called 911 to report a suspicious person in the neighborhood and minutes later dispatchers received several calls of shots being fired in the neighborhood.

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.

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.

The Sanford Police Department refused to release 911 calls by witnesses and neighbors.