Which could utterly destroy one's life.
I should have clarified better, but I meant utilizing a firearm in an instance where the law deems it illegal to use deadly force, but it would be deemed by most moral people to be the right thing to do. I meant that in defense of another, but I am not read up on all of the states' self defense laws to come up with a situation that would apply.
I purely meant that repercussions of the law shouldn't be a deciding factor when intervening to save someone's life. The details are different and deadly force was not used, but SFC Martland's case comes to mind. Though, admittedly, I've never had to deal with repercussions of that nature so, YMMV.