It wouldn't surprise me if Martin attacked Zimmerman for "dissing" and tried to inflict a beating he wouldn't forget, at the end of which Zimmerman pulled out his concealed weapon to avoid being pounded to death.
That's where the evidence is pointing. Add in that Zimmerman was calling for help, and neighbors heard him. Nobody came to his assistance. i don;t know how long he claims to have "waited" for assistance, even a shouted out "STOP THAT!" from one or more people who live in the vicinity. He's justified in using deadly force even is he's not in fear of his life - what he has to apprehend is a threat of serious injury.
What fascinates me is that the media can be so reckless in fabricating a highly incendiary false narrative, and not hurt itself in the process.