The last information that we have about martin’s actions before the 911 calls reporting the fight is from zimmerman’s recorded call. In that call the last thing that zimmerman said about martin is...”he ran away.”
The last thing Zimmerman said about Martin is “I don’t know where this kid is” meaning he had lost him. So much for Zimmerman initiating a confrontation.
http://www.documentcloud.org/documents/326700-full-transcript-zimmerman.html
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I wrote that the last thing we know of martin's ACTIONS is that he ran away.
And, since the moment when the two found themselves face to face was unrecorded and, as far as we know, unwitnessed, nobody can say with any certainty (speculation but not certainty) who initiated the confrontation.