"That's actually my fault...."

I pick up my son from school every day. The ride from school to home takes about 30 minutes. We learn a lot about each other during our 30 minute rides each day. I get to say things like "How was your day?" and he responds to everything with "Fine". I change it up to elicit other answers by asking "What was your least favorite event today"? etc.

Today we had a little discussion at the end of the commute, prompted by me spying a newspaper up on the roof of our house.

Me: "Why is there a newspaper on the roof of the house"?
Him: [Laughing] "That is actually my fault..."
(Honestly, I'm amazed he took responsibility for it.)
Me: "I know it is your fault, when there is a newspaper on the roof, it usually isn't anyone else's fault. How did it get there"?
Him: [Still Laughing] "Well, you know how I am usually pretty good at throwing things right where I want them..."
Me: [Interrupting him]: "Let me rephrase your statement, you are NEVER good throwing things right where you want them."
Him: "Well, not backwards maybe but..."
Me: [Interrupting again] "No, not ever."
Him: "Well, ok, but I was skateboarding down the driveway when there were no cars there, and I picked up the paper and tossed it backwards, and it landed on the roof."
Me: [Just staring at him]
Him: "I tried to get Michael to help by standing on the chair with the broom and scraping it off, but he wouldn't stand on the handles."
Me: [at least they aren't fighting....and I decide to let it drop there]