I hope this was an isolated instance of theft. I'm sure that you have asked him if he has done similar things like this before. If he has, this would be an appropriate time for him to unburden himself and to confess to any other such illegal activities. Confession is good for the soul and you need to promise him forgiveness and understanding, along with your expected disappointment and shock, if he chooses to confess other illegal acts.
Now is the time to offer him a chance for redemption in your eyes. He has betrayed the trust and lost the respect of the store-owners, his co-workers, and his family. That loss should be ample punishment for a young man who has brought shame upon himself and his family. I would refrain from any home punishment. I suggest that you have a continuing series of discussions with him about his values, his level of remorse, and how he plans on living differently to reestablish trust with you and the other people that were affected by his crime. By learning from his poor judgment in this matter, he may become an even more moral man of character. Continuing to shame him will not help him recover and improve. Reminding him of his innate goodness and allowing him to prove his worthiness once again should be the focus. Help him reclaim his dignity. He will learn much about himself and his family by your response to this unfortunate incident.