As to Zimmerman never calling for medical aid, for God's sake, the police were there in just a couple minutes. He was a complete wreck. Ever have your adrenalin pumping so hard you think your heart's going to leap out of your chest? Unless you've been there, you just can't imagine the physical assault that adrenalin rush/ebb puts on your body. He wasn't even thinking -- if what he says is true.
I really think you need more perspective. This isn't cut-and-dried either way. There's too many unknowns.