@roger,
The police didn't say how many times the attacker had been shot, only that he was dead (still holding the knife). The victim appears to have fired until empty and I'm guessing stress could have something to do with that (he was being assaulted with a large knife/fear for his children). I don't know all the gun laws in all states, so you might be right on the 'excessive force' issue.
Anyhoo...the attacker seems to have picked the wrong guy to mess with.