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?
"If it’s true that our species is alone in the universe, then I’d have to say that the universe aimed rather low and settled for very little"