Tell your mother to hide her valuables (just in case). He needs an addiction specialist in the area, pronto. Your mother should also find support.
It is so sad what you are going through. My sister is 28 and an addict for nearly 14 years now. If only my parents had been as engaged when it started as you are!
Because it's my sibling who is the addict, I want to gently remind you not to forget about your other children. They need help to get through this as well. If your kids are young, they shouldn't be around your addict son without supervision. My brother and I were sort of forgotten after my sister started to get bad. And she used to beat us up and steal from us, our parents did nothing. Our safety took a backseat to "curing" my sister.
Good luck to you!