Exactly what would have been you course of action? Knock on the door be told nothing to see here and move on? A terrorist is on the loose and has proven he has no regard for human life. He could have unknown people assisting him or could be in a house threatening a loved one in order to get the occupant to tell law enforcement all is well. Seriously what was your plan of action?
It is well that war is so terrible -- lest we should grow too fond of it
Robert E. Lee~