While I applaud the guy for carrying, it's a good thing for him the bad guy ran away when he saw the gun. Had the victim followed through with his plan to "ventilate" the bad guy, at that point of the situation, he likely would have done some serious jail time. Once the bad guy took the wallet and moved back over to the front door of the office, away from the victim, there was no more threat to validate the use of lethal force. When the victim got out of his truck with his gun and approached the bad guy to "ventilate" him, it would have been murder. That would have been a bad situation. I hope someone talks to that man and explains the law to him, it would be a shame for the "good guy" to become the "bad guy" in such a situation.
EDIT: Never mind, I missed a key detail on first hearing the story. My bad. His good!