Can you use a firearm to defend yourself against an unarmed attacker? Should you?
There are a lot of misconceptions about this issue. Massad Ayoob does a good job explaining it here…
“Disparity of force was a key element here. It means when an ostensibly unarmed man is so likely to kill or cripple you, his physical advantage becomes the equivalent of a deadly weapon, and warrants your recourse to a gun or knife or whatever in self-defense.”