Hard to say exactly what happened. In Zimmerman's defense, Martin was supposedly an athlete, and could have easily outrun Zimmerman, who's kinda fat. Makes me think Martin provoked him, or something. Clearly, there was something that lead to their altercation. Zimmerman didn't shoot out of the blue, and there's numerous 911 calls that describe the two fighting. It's what happened between the time of Zimmerman calling 911 stating he's following him and the gunshot going off that's going to make or break this case, and so far I don't think anyone has any detail on that.
It is kind of interesting I think.