Martin was on top of Zimmerman, beating him in the head.
That’s why no charges were filed.
Of course the reason he was on top of him beating him in the head MAY have been that he feared for his life when approached at night by an armed man.
Had the kid shot Zimmerman in fear for his life, he might have had a decent defense under Stand Your Ground. It doesn’t seem reasonable that he should be presumed at fault because he wasn’t packing.
If the two grappled over the gun and Zimmerman got shot, the kid would have a very good case for self-defense, probably. It doesn’t seem a good idea to have laws in place that allow a killing to be judged self-defense regardless of which party survives.
I realize we have no-fault divorce now, but no-fault shooting probably isn’t a good idea.