I'm the first to go to bat for combat soldiers in very grey situations where it is hard to tell friend from foe...in this instance though, it seems pretty black and white. If they were simply fragging and clearing I wouldn't condone the action but I can understand it...the fact they were all shot in the chest and head means it was in close quarters and they likely were able see exactly what they were doing.
Where was the leadership on this? I understand in the heat of combat emotions run high and soldiers are tempted to do things they would not normally do...that's why we have experienced leaders that are supposed to channel this aggression in the appropriate way...not unload on a bunch of civilians who were obviously not caught in the cross fire. Even after it happened, if the leadership had taken an active role in investigating this matter before it reached the theatre level leadership it would have done a lot show that the US military does not condone the action and that we punish those who operate outside the rules and regulations set forth to prevent such a thing from happening.
I hate to be a Monday morning quarterback because I was not there when it happened...to me though, the evidence is pretty damning...