What's an appropriate punishment for an 8 year old firebug?

My 8 year old son got in our truck today and lit some “fabric” on fire. He was attempting to make a fireball, something he’d seen on a youtube video. I guess he knew there was a lighter in there, I was gone at work and the details are still unclear. He had told his dad he was going out to ride his bike and came in 10 minutes later saying the truck was on fire. The whole side of the passenger seat is melted, the thing you fasten your seatbelt to is melted, a large portion of the carpet beside the seat is burned. My husband said it was in flames when he went out there to see what was going on.

What do you feel is an appropriate punishment. I had no idea he was looking at stuff like that on youtube, needless to say, not my finest hour as a parent. As it stands now he is banished to his bedroom for the next 2 days and is off the internet until further notice.