Silly question, really...
Try to find someone with certified "combat experience." Known two. Both said the same thing. Anyone who claims to enjoy combat is #1) LYING!!! or #2). on the loose from a "nut house."
What "gets lost" in the discussion is the effects of chemicals. In combat the consumption of liquor is legendary, as available. Other chemicals are less discussed. Opiates in Viet Nam. Then there is adrenalin. In civie situation, who knows what the BG has consumed? One would hope you are not near "drunk" and armed...
POINT: You shoot the BG with a shotgun or ??? and it may just "make him mad." Seldom will he be alone. Make his friends mad too. YES, he will die within 30 days, maybe 30 minutes BUT what will he and his friends be doing in those 30 minutes... ???
And you try to convey this to a jury. (ha, ha).
You are much, MUCH better off to not fire and avoid the "paperwork." Hit 911 on a couple of cell phones and let them find you HIDING! and deal with the BG(s)... If you shoot, you shoot until the "threat" is "over" or you run out of ammo.
Bodys that have been shot do not fall down and lay still like in the movies. [SURPRISE!] They may become very "spastic." You cannot be sure if there is still "intent" so you shoot again, and again... Parts may come off. Blood may be everywhere. The good outcome is where the blood is not yours. Vomit, maybe, but no blood.
Doubt me? Find a copy of Audie Murphy's biography(s). He probably killed more white men in the 20th century, legally, than any other. Where? European Theater of Combat, WW II. Picked up every combat decoration available including the Congressional Medal. You can catch the movie, "To Hell and Back" in which he starred. Part that gets left out is in the books. Spent the rest of his short life sleeping with a pistol under his pillow. 1911? Lost 3 wives who got tired of being pistol whipped in his nightmares...
You MIGHT want to save that last bullet for yourself. luck.