Your arm isn't going to immediately be disabled, you will still probably be able to shoot after getting hit in the arm, of course you won't be deadeye accurate and won't be able to for more than a couple shots but, with the adrenaline pumping through your body the feeling won't be instant.
use the gun as a way to keep them from bolting until the police arrive. only shoot if they pull out a weapon
I'm talking about if someone has a weapon and is inside of your house, there's no reason to kill someone if they're unarmed.