^^^^^^^^^^^ This
I don't threaten deadly force if I am not justified in using deadly force.
There is a subtle distinction here. I am not saying that every time I pull my handgun that means I have to shoot it. But if I pull my handgun, I am going to be able to articulate why I was legally justified in using deadly force regardless of whether I had to shoot or not.
As a corollary, if I am legally justified in using deadly force, that generally means I am in fear of death or serious bodily injury, or it is "presumed reasonable" to believe that I am in such fear. If I am in fear of death or serious bodily injury, then the police need to be notified of same. If I do not bother to notify the police, I could be setting myself up for someone to counter-argue, "he wasn't really in fear or he would have reported it."