Really? Are you serious?
Kid is walking home with some skittles and tea, that he bought at local convenience store. There is nothing to suggest the kid was up to anything more than that.
Zimmerman notices the kid and phones the operator and tells the operator explicitly that he wasn’t going to let the kid get away and gets out of his vehicle to confront the kid.
And you still don’t know who likely attacked first?
The law defines first contact of any sort as attacking. So much as a touch on the body is defined as an attack. How many kids, when confronted by a man with a gun are going to throw the first punch?
Many presume the law was written for the sole purpose of protecting gunowners from legal repercussions if they end up shooting some bad guy. Actually, this law protects unarmed victims from guys with guns as well. They don't have to stand there and take it. If they feel in fear for their lives they can mount a resistance using any means feasible.