First of all, what he did was wrong because he didn't follow the order of his parent's but now that he already committed the mistake, I think it will now be easy for him to commit another mistake which is to lie, just in case his parents find out about the money. Im sure there must be other profitable activity that is allowed in his country like investing or trading. He can just say that he got the money from those sources. There might still be people who can feel guilty right after making one mistake and they will confess it right away. They think this will lessen the punishment that they will be getting.
Such mistake I don't know if it is a good mistake or bad mistake but the important thing is that he already has a source of livelihood with him. He is lucky to win that huge sum of money capable to change his life for good. If he invest the money rightly in a profitable venture, his parents one day will forgive him after all he didn't steal it or used gun to rub from off their money. They are still family and family is always a family, things as such will not cause them apart and huge money is involved that is enough to still put smile on their faces on the long run depending on the economic status.