In his version of events, he had turned around and was walking back to his SUV when Trayvon approached him from behind, the two exchanged words then Trayvon punched him in the nose, sending him to the ground, and began beating him.
Zimmerman told police he shot the teenager in self-defense...
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.
UPDATE -- A later story adds "Zimmerman told police he he'd lost sight of Martin and was heading back to his car when the youth suddenly stepped into his path. According to the Sentinel, Martin asked Zimmerman if he had a problem. Zimmerman said no and reached for his cellphone. Martin then said something like, "Well, you do now" and punched him, according to the Sentinel's sources............
And though it doesn't really sound true to me -- an unarmed teenager approaching, confronting and then attacking a larger man who'd been following him? --
the Sentinel story tells us that "much of it has been corroborated by witnesses, authorities say."