Zimmerman's story has not been well circulated, but it has a series of events, ending with the shooting. His version has him taking a beating, no effort on his part to use deadly force. He shifts his body so his head would be slammed to the grass instead of to the sidewalk, and in shifting, exposes his holstered pistol. Details murky here as to who grabbed for the gun first, but on seeing the pistol, Trayvon Martin uttered a death threat. There was a struggle over who would possess the pistol. This is after taking 45 seconds - 75 seconds of beating.
-- Martin got exactly what he deserved --
I think we'll find that was the UNANIMOUS decision of the Sanford police.
Think the “murky details” might be cleared up with forensic test revealed: Who has powder on hands, angle of gunshot, etc.
Until that information is released, people can/will speculate.