Human body has a great way to not allow pain to stop a bad guy. Adrenalin will keep a bad guy moving till you hit spine, brain, or heart.
Was the Shotgun even loaded? I guess its not like the movies. Bad guy goes down and continues to unload his weapon. One 9mm shot and the guy was incapacitated. Would have been the same with a 38 or 50. Bad guy would have dropped his gun and ran like the coward he was. He would have been in more pain in his hiding spot with a 50 than with the 9 wound though.
Great outcome for sure.