You assume that he even went towards his car.
If he, disobeyed the dispatcher, then he is the aggressor for not following the direct order from him/her. He pursued when clearly instructed not to, escalating the immediate situation. Therefore, he is the attacker, putting Trayvon at risk, and making himself open to whatever charges put before him. He would have not needed to discharge his weapon if he had heeded the order from said dispatcher, and let the professionals handle the perceived threat, rendering this an open and shut case.
Zimmerman, with a 2nd degree murder charge, should be imprisoned for whatever the law alllows since he did not follow a direct order from a sanctioned dispatcher and instead decided to take the law into his own hands. The result: an innocent teenager who had such a deadly weapon as skittles.
For all Trayvon knew, he could have been a predator who preys on teeange boys, but when someone follows me, I make damn sure they better keep away. Otherwise they will get the beatdown they deserve.