Zimmerman claims he had lost sight of Martin (which is supported by the call to dispatch and by Martin telling his girlfriend that he had lost Zimmerman), and that he was on his way back to his truck (presumably to meet police where he told them he’d meet them). THE BURDEN OF PROOF IS NOT ON ZIMMERMAN. If you don’t believe him fine, but offer proof to back up your contention that his story is false.
See my post 132 about criminal law and self-serving statements.