I don't know what you mean by this.
I found it interesting that a witness says the kid attacked Zimmerman, who had grass stains on the back of his shirt/jacket and a bloody nose. If that is all true, and the police responding made note of that, it appears they decided zimmerman was attacked.
But we don't know what Zimmerman may have done to start the confrontation. It's clear that Martin went into "beat down" mode, but did he jump Zimmerman from behind, unawares? Or did Zimmerman, after chasing him down, try to physically stop Martin?
And you are right - we don't know what else happened in that altercation. But I'm going to assume the police were satisfied that zimmerman was in the right on this, and that the witness felt the same way. I do agree that normally neighborhood watch folks are not armed and are just there as a deterrant, not as an armed guard. The whole situation is insane