"...the way in which the students apparently knelt down and accepted their deaths."

that is crap! He stepped in and started shooting! You would jump up and head FOR him? You'd simply be 2nd in his sights. 'Maybe' if 10 people all rushed him.....but do you really believe you can instill THAT reaction in a random group of students?
Now if he had come in with a knife.....or a baseball bat....