Just because you may be legally justified for pulling out a gun, doesn't mean you need to shoot it.
If you do shoot it, just make you are the last one standing and the other guy isn't around to refute your side of the story.
From my little understanding: You always get prosecuted and the only way to get away with it is by being in grave danger that u had to shoot the guy.
Not threaten because that means u weren't in grave enough danger to pull it out I've read about it in books that describe it in more detail but that's the general idea.
( of course it all boils down to how aggressive the prosecutor/ jury are)