It appears to be a little more complicated than that. Trayvon Martin's 911 Calls: New Tapes Trace Teen's Final Moments
There’s really nothing more here than some mall ninja without the will or physical acumen to run down a black kid who he deems suspicious. There was no weapon on his person according to all accounts, and Zimmerman used racial epithets to describe the kid/situation on the phone with the police, regardless of whether or not he wanted those epithets to be recorded.