it's the exact same situation as the greyhound bus beheading that happened in canada a year ago. police came in, surrounded the bus and spend hours till they managed to cuff the guy who everyone on the bus saw what he had done. (when police came the other people had managed to lock him inside the bus) now tell me if telling the guy once to drop his knife and get on the floor and subsequently shooting him when he tries anything funny is not much better than half decade long trials and psychic evaluations that the guy is gonna go through on the taxpayers dime.
Even if you embellish numbers and say Bush was "responsible" for, 2 or 2.5 or even 3 million people, he is still a fraction of either Stalin or Hitler.