If he's still standing with a weapon in his hand, you keep shooting. You don't shoot once and examine his demeanor. You keep shooting.
If he goes down but still has a gun in his hand, you keep shooting.
You stop shooting only when either he is visibly no longer a threat, or you're out of ammo.
Or as my Marine buddy says, “The target either changes shape or catches fire.”
Yep. When in doubt, mag dump.
Your life is worth a few extra rounds down range...