First, try to call the listing agent and ask them about why the home was sold for such a low price. If they refuse to tell you, or if the story is dodgy, it might be a good idea to look into the trustees of the parents’ estate, and also look into who the guardian of this man might be.

If you can’t get anywhere with this, it might be a good idea to report it to the California Department of Real Estate, at least for a start. After that, the police, though I’m not convinced they’ll do much. Definitely worth escalating this, IMO, because there is nothing worse than people taking advantage of those who have no means of defending themselves.

If you need help with any of this, please PM me. I will help in any way possible.