One thing to remember is that we, when viewing the video, are not in a vibrating helicopter. It would be nice if we could know, for certain, what the Rules of Engagement were. On MSNBC a Colonel claims they were "You may engage persons who commit hostile acts or show hostile intent by minimum force necessary." and "Do not target or strike anyone who has surrendered or who is out of combat due to sickness or wounds." Wikileaks co-founder notes that the helicopter pilots are hoping the guy picks up a gun so they can shoot him.