A.J.
You say he knows it's wrong. In what way did you teach him in no uncertain terms with dire consequences the very first, second, third time he ever tried such things that it was wrong, until he learned self control for the sake of personal preservation at first, which therefore set the habit to not do it, until his conscience set in and he "knew it" on his own? (He's now old enough)
If you have been too lenient in real consequences, or only TOLD him it was wrong many times, he probably doesn't know.
Maximum consequences are appropriate. Every time. Even compounded ones (returning item, PLUS apologizing, PLUS firm DISCIPLINE, PLUS hard chores to do, PLUS removal of privileges until earned back over x amount of time all in one shot) following a calm explanation of how HIS actions have caused HIS very firm consequences. Don't fear you child will get even worse and therefore let him get away with it.
Don't fear your own anxiety, be proactive. Like with anything else in life, if you are ADDRESSING it, your anxiety will lessen.
He's getting old regarding shaping his character, so don't delay!
This book is GREAT for this age: Back to Basics Discipline by Janet Campbell Matson.