This will all be cleared up during trial, but ABC News has purportedly received a 'photo' that was 'taken' by a witness on the scene, allegedly unaffiliated with law enforcement.
The story goes that this guy took this photo approximately 3 minutes after Trayvon Martin shooting and supposedly was told by Zimmerman to call his wife and tell her he 'shot someone'.
(Firstly, why would Zimmerman tell someone other than law enforcement to call his wife?? Why ask a stranger to do that?)
Anyway, here's the photo. My first impulse was that the photo was 'shopped because the blood trails looked odd. And the cut seemed more like a lateral laceration and not a blow to the back of the head. But again the photo could be legitimate, but it doesn't mean the shooting was self-defense.