So far, the only source I've seen for that version is Zimmerman himself.
All the other accounts come in mid-battle, after Martin had achieved superiority and before Zimmerman invoked the nuclear option. There is no independent witness as to who initiated the violence.
The guilty or not guilty verdict depends on who started the violent confrontation. Given the evidence so far, I think, if I were on the jury, I'd have to walk Zimmerman, albeit reluctantly. It comes down to the difference between "preponderance" and "beyond a reasonable doubt".
Let’s ponder the evidence then.
http://www.sanfordfl.gov/index.html
Listen to call 1, that’s George’s only call.
Point 1: Where at any point in this call does george say “f***ing coons”?
Point 2: George begins to run after the suspect or at least give pursuit at faster than walking pace. The operator asks him are you following him. Yes, replies George. Ok, we don’t need you to do that. OK. He ran - past tense implies that Trayvon got away as opposed to he’s running which was stated earlier. The running stops, this is apparent because the noise of running stops. George obeyed the request.
At this point the operator asks where do you want to meet the officers and George says something about his truck. I am going to theorize that at this point George would be returning to his truck, because he is no longer chasing Martin, and I expect that he intended to meet the police there, however, this is my speculation.
In the very least we know that at this time he was no longer running after Martin, and he also stated that martin “ran”.
I cannot and will not state that Zimmerman started any sort of violent confrontation by evidence of this phone call.