Zimmerman’s response to the dispatcher (not an LEO) was “OK.” People assume that Z continued to follow Martin, but is that in fact true? Martin was bashing Z’s head against a concrete sidewalk and not soft grassy turf. The evidence is clear. Therefore I can only assume that Z left the site and was returning to his car parked along the sidewalk. Martin turned around and approached Z from behind and initated the attack which ended up with Zimmerman on the ground/sidewalk with his nose broken and his skull cracked.
Check this breakdown out. It has the timeline combined with the phone call.
http://www.wagist.com/2012/dan-linehan/evidence-that-trayvon-martin-doubled-back
In the same hearing prosecutor Bernie de la Rionda states that Martin bought a can of tea at the 7-11 and Gilbreath agrees, under oath. We know Martin didn't buy tea.