One of the quotes from a professor I had really stuck in my head. He was giving a lecture on home defense, he was in this situation first hand. He shot a man breaking into his house in the middle of the night in a rural town. He never was charged with any crime, but when asked by the detective why he shot the man 11 times he said "because he quit moving before I could find my second clip". This man is a 30 year veteran police officer, was the police chief for many years, and now teaches college criminal justice classes.
The one thing he really reiterated and kept telling us to always remember is if someone is in your house and you need to fire a weapon to protect yourself, NEVER STOP SHOOTING UNTIL YOU RUN OUT OF AMMO OR HE STOPS MOVING. Even a dying man can reach up and put a round through your skull, and it only takes one. If he stops moving, you keep that gun pointed at him and stand where you are until the police arrive. It is not your job, nor your obligation to see if he is dead or alive. You threat him like he can kill you at any second until the police arrive.