When one pursues his victim, the FL law does not apply - as we heard on the 911 call, Zimmerman told the police he was following the 17yr old kid and at which time Zimmerman was specifically told by the police not to do that.
Also, using common sense if someone had his "head slammed into the concrete" there would be serious injuries that could not simply be treated in the back of a cruiser by a fireman - he would have been transmitted to a hospital.
"If you don't think too good, don't think too much"
-Ted Williams