Agreed, on the first comment. It's still mostly Zimmerman's fault. Keyword "mostly". From everything that I've read, that seems like the most likely scenario of what occurred. Perhaps not, perhaps Zimmerman instigated everything, but from the information available out there it's at the very least ambiguous who instigated the fight (even if Zimmerman created the situation by wantonly following Martin in the first place).
On the second part, my hypothetical serves to underscore 1) that if Zimmerman wasn't lying to police about what happened (a big "if" to many), then Trayvon through his own brashness helped escalate the situation, and 2) that really this is an issue about guns not race.
The information available is limited to Zimmerman's account, which is highly suspect, and some hearsay from the girl on the phone, which may be admissible in court since Trayvon is dead but is still secondhand at best. Even so, I don't find it all that ambiguous. Even if Trayvon initially turned around and confronted him, I have an extremely hard time believing that the armed volunteer watchman who was stalking the kid because he found his skin color suspicious responded coolly and appropriately.
And to your second part, this is absolutely about race, and I don't think it's about guns. But it's also, and in some ways more importantly, about SYG, and the fucked up precedent it has set that as long as you kill the other guy (regardless of what you use to do it), you get the full benefit of the doubt that he was the one who started the fight. Which is an absolutely horrible message for the justice system to be sending out. "Well, you committed battery, but if you kill the guy you'll probably get off with nothing!"