Who Can You Tell?

I'm pretty sure my dad has a gambling problem and who can I tell?  My mom would freak--she doesn't handle stressful situations at all.  My dad would deny it.  I don't have any siblings.  I feel like crying when I see the stacks of lottery tickets and hear about the trips to the Indian casinos.  It's pitiful.  He's spending all his retirement money.  I think things are getting desperate.