That football player attacked him.
Also, he wasn't under any obligation to follow the dispatchers advise.
Lee, the police chief, said in a statement that the police dispatcher's "suggestion" to Zimmerman that he did not need to follow Martin "is not a lawful order that Mr. Zimmermann would be required to follow."
"Mr. Zimmerman's statement was that he had lost sight of Trayvon and was returning to his truck to meet the police officer when he says he was attacked by Trayvon," Lee said.
'Stand Your Ground Law' at center of Fla. shooting - Yahoo! News
Here is some more evidence that those not participating in the other thread may not be aware of.
"The guy on the bottom, who had a red sweater on, was yelling to me, 'Help! Help!' and I told him to stop, and I was calling 911," said the witness, who asked to be identified only by his first name, John.
John said he locked his patio door, ran upstairs and heard at least one gun shot.
"And then, when I got upstairs and looked down, the guy who was on the top beating up the other guy, was the one laying in the grass, and I believe he was dead at that point."
Man shot and killed in neighborhood altercationSanford police detectives claimed:
It was prosecutors who advised them there was not enough evidence to win a manslaughter conviction.
Lead detective played recording of screams for help and Martin's Father said voice on 911 call was not his son's.
Sanford Police Speak Out In Trayvon Martin Case - Yahoo! News