It wasn't. Sanford PD didpatcher logs the xaal from Zimmerman at 12 seconds past 7:11PM. logs off at 15 seconds past 7:15PM
Martin was on his phone to his girl from 7:12 to 7:16, phone call ends just after Zimmerman and Martin meet.
Police arrive in area at 7:17PM. Find Zimmerman and Martin's dead body sometime between then and c.7:20. EMT;s pronounce Martin dead at 7:30PM
Some of us are having a hard time fitting Martin stalking and attacking Zimmerman, a major fight, and the shooting in the space of 1-3 minutes.
One round in boxing is 3 minutes. Try to imagine 3 minutes in the ring with anybody. One minute of intense fighting can be lethal. My guess is thats about as long as this fight lasted. About one or two very long minutes for Zimmerman as he was on the bottom and getting the stew kicked out of him and screaming for help.
If there was any probable cause the police would have arrested Zimmerman by now and the DA would have filed charges. Since this has not happened the furor will continue for awhile and then die down when the authorities finally have a news conference and announce that no charges will be filed and the case is being closed. The DA is not going to go to court knowing they have a losing case.