When my girls were young, the worst thing they hated to do was to have to apologize. So, whenever they were verbally abusive to someone, or whatever, I attempted to "talk" the situation out with them, then I would march them to the person and have them apologize for their part.
Your son? Well, I'd instruct him that there are rules we all have to live by, and how would he like it if some stranger came into his bedroom and stole something from him.... then, I'd march him down to the store and make him apologize to the manager and the security guard who nailed him.
Just a thought... he's surely NOT forget it any time soon.... apologizing is like the lowest of low's to kids... but, a great learning experience!
PitterPat