Given all known evidence (what John saw, the wounds, single shot fired, the screams, GZ calling police ahead of time, etc etc etc) there is no way to doubt that this was self-defense other than via ignorance of that evidence, racial thinking, overabundance of emotion or some combination of those.
And no I'm not being overly simplistic, this is actually really, REALLY obviously self-defense.
You're really, REALLY obviously a shill who's being paid to defend Zimmerman. John recanted, there is no proof the screams are Zimmerman's, Zimmerman's story has changed more than once, Zimmerman has a documented history of violence.
How have you not been fired? You're really terrible at this, Mr. "I'm a liberal, but that thug deserved it."