Holy Hannah, here's a new twist. The surveillance video shows that three teens wearing shades and with their faces covered entered the 7-11 a minute or so after Trayvon left. They stayed for a couple of minutes then exited.
Just as the three were leaving, it looks like Trayvon can be seen outside the store walking away. He may have looked back in their direction as he was leaving.
http://www.youtube.com/watch?v=_DBHAigFmvo