I believe TM was beating on GZ as shown by the evidence.
The frustration I'm having is that no one can testify to what happened PRIOR to this altercation. We will never know if GZ made TM fear for HIS life and that is why he was beating him. The only one who can testify to that is dead.
My other frustration is that if GZ would have just left TM alone, TM would have gone home, shared the skittles with his little brother and gone on with the life God had created him to have.
TM wasn't out "looking" for trouble that night but GZ certainly was.
I'm pretty sure, IMO, that anyone involved in Neighborhood Watch looks for trouble. They are on the look out for trouble. That's what they do.