I am sorry to hear that sad news.
That is the worst thing that can happen to a gambler. Isolating yourself from friends and family and then committing crimes. Gambling addicts have no control over their actions. So, it is up to us, their friends, to intervene whenever we notice that our friends are already too deep into gambling. If we caught it early, we can still save gambling addicts.
I think that some years in jail would be the right punishment for such persons and also there to be treated for their illness.
They have to face the consequence of their criminal acts but I do not think jail is the right place for them to fix their addiction. They need psychological help.