He misunderstood what was happening, I don't think he did anything "wrong".
I was intrigued about the time Trayvon got caught in school with the jewelry, the teacher noticed Trayvon was "acting suspiciously" and investigated, and found the jewelry and screwdriver in his possession.
I'm bringing this up because I wonder what the teacher saw? What GZ saw? Both seem to characterize Trayvon's movements the same way.
If the case was that Trayvon was merely running in GZ's direction - as a pure coincidence to get out of the rain for example - and GZ mistakenly shot and killed him, that would be horrific and would make GZ feel remorse.
He was being punched in the head. I really don't know how much remorse I'd feel for shooting some guy who was on top of me pounding my head. I'd feel sad for his family, for sure. My mindset is it's likely one of us isn't going to live through this incident, and it's going to be you.