From the Orlando Sentinel Article:
There is about a one-minute gap during which police say they're not sure what happened.
Zimmerman told them he lost sight of Trayvon and was walking back to his SUV when Trayvon approached him from the left rear, and they exchanged words.
Trayvon asked Zimmerman if he had a problem. Zimmerman said no and reached for his cell phone, he told police. Trayvon then said, "Well, you do now" or something similar and punched Zimmerman in the nose, according to the account he gave police.
Zimmerman fell to the ground and Trayvon got on top of him and began slamming his head into the sidewalk, he told police.
Zimmerman began yelling for help.
Several witnesses heard those cries, and there has been a dispute about whether they came from Zimmerman or Trayvon.
Lawyers for Trayvon's family say it was Trayvon, but police say their evidence indicates it was Zimmerman.
One witness, who has since talked to local television news reporters, told police he saw Zimmerman on the ground with Trayvon on top, pounding him — and was unequivocal that it was Zimmerman who was crying for help.
Zimmerman then shot Trayvon once in the chest at very close range, according to authorities.
When police arrived less than two minutes later, Zimmerman was bleeding from the nose, had a swollen lip and had bloody lacerations to the back of his head.
In a statement released by the Sanford Police Department, they indicated that the information was not released officially and anyone releasing information could be subject to displinary action up to firing, but then they said that,
"the information provided in the article is consistent with what the Sanford Police Department provided to the State Attorney's office."
FWIW...WABC news just reported that the homicide detective who interviewed Zimmerman didn't buy his story and wanted to charge him but the county prosecutors said that they didn't feel that they could convict on the evidence.
As I said earlier...I don't think that he will ever be charged...precisely because there are no witnesses to the start of the fight.
There may be a civil suit but who knows how that would go...