What sort of punishment should a 10 year old get when caught smoking weed/pot?

I just caught my 10 year old son smoking a joint in his bedroom when he was supposed to be cleaning it. I'm completely beside myself as far as a good punishment is concerned. I already told him he's not allowed to go on Facebook for the rest of the night but I feel something else needs to be done about him smoking weed at such a young age. I was 12 before I started smoking cigarettes and when I was caught at the age of 14, my father made me smoke the entire pack and get ill so I knew to quit. I know he listens to a lot of that Snoopy Dog rapper guy and he likes to promote smoking weed and other gangsta stuff. Besides losing his ipod and Facebook privileges for the night, how should I punish this kid(he claims he borrowed the joint from my husband's stash but he claims he isn't missing any so he's also lying to me).