These events aren't nearly as black and white as you think they are. There are a lot of ways to fuck up. You can potentially get shot by 1) the shooter/shooters 2) LE 3) another dude like you. You have to avoid shooting 1) another good guy 2) everybody else.
If you have a clear understanding of who the bad guy is, an opportunity to shoot, and the ability to hit only him, go for it. You could also save some innocent lives by keeping your head and getting them out of harm's way.