I doubt that there is legislative language but I can assure you that it is a prosecutor's issue and he or she can nail your aXX to the wall for murder if you shoot to kill after the threat is negated.
I can distinctly remember the instructions given to me by an NRA instructor, who was himself a retired LEO. He said you keep shooting until the threatening person falls to the ground and then you stop. You definitely stop at that point. Any further and you can be charged with murder. And I think Mr. Smith will be charged with murder.
Like I have stated....this man spoke too much. He should have shut his trap.