If you're acting on behalf of the neighborhood watch, it would seem logical to identify yourself as such to avoid any confusion.  If Trayvon would have known that he was acting on behalf of the neighborhood, maybe he wouldn't have responded in a "none of your business" kind of way and volunteered that he was staying with his dad or whatever.  But it does seem likely that because the information wasn't communicated, Trayvon felt threatened by some guy following him...and responded in a hostile way which resulted in George also responding in a similar way.  Unfortunately, Trayvon was at a disadvantage in this altercation and lost.  So, is someone at fault?  With only one side of the story, it's difficult to tell who started the violence.  But whoever that is...I'd say is to blame.  Violence isn't the solution to crime.  And it doesn't make sense to me that someone trying to prevent crime is seeking out situations to commit a crime.