You're probably right. Ideally, no one would die by violence ... but they do. And of course, although we can identify gravely sinful actions, no human being can know the state of another's soul. Only God can.
So we (as societies) have to make decisions the best we can. Do we not fight a war because we might kill someone, who will then go to Hell? Or if we don't fight a war, will a bunch of different people, our own citizens, be killed, and some of them go to Hell? Do we not execute an impenitent murderer, or do we give him the opportunity to kill others?
This is a very strong concern for me, as we both know it does happen. I agree with your post that those are tough decisions for a society to make, which is why my support for the death penalty is only half as strong as my opposition to abortion.
You raise an interesting notion above. What would you say about a penitent murderer sentenced to die? The best example I can think of is Karla Faye Tucker in Texas. She "convinced" me that her faith was legitimate. I remember struggling with what I would do in then Gov. Bush's place.