look I'm talking about the real world example you gave me.

The guy is inside the van and you think there is a bomb inside that will kill a lot of inoocent people. You has a cop or the bombsquad or whatever have one chance to stop him. That's the situation, correct? Now I can't be 100% sure that the guy really has a bomb unless I open the door. unfortunately, if I try to do that with him still alive, and there is a bomb -- he presses the button and probably you will be seriously injured and besides which at least a dozen other people die. Annouce yourself and he'll probably push the button rather than be taken. You can let a person sit in the middle of a neighborhood with the potential to take out dozens of people (which your intelligence has a good reason to believe in this example). If the only way to prevent a tragedy from happening is to shoot the guy, then that's how it is. The alternatives are not good. I admit that. But the consequences of announcing yourself to the guy in the van is possibly the deaths of a dozen people including the guy himself. the consequence of a sniper taking him out is that AT WORST one person dies and there is no bomb.

Yes in a perfect world such choices would not be neccessary. But that's not real life. I can't just redo that situation until I come up with the perfect answer. I don't think I could live with myself if I could have prevented the bomb from going off but didn't because I didn't want to risk not following procedures.