do you ever wonder why?

I don't know what it is about my son. He is generally a good kid but from time to time he does some things that make me just ask...WHY? The other day he and his friend John were playing and John comes running downstairs with a little worried look on his face and says, "Jake thought it would be funny to throw a hot wheel at the window the hot wheel broke and so did the window." OK I was on the phone at the time put I picked up broken and widow out of that sentence and rushed my way through that phone conversation to go and evaluate the damage. He couldn't have broken the window with a hot wheel, what is John talking about?! Oh it was broken all right, with a hole and everything, cracked to all four corners, I think actual steam may have been coming out of Mike's ears at this point. We were both very calm though, looked at Jake and asked him why he did it and got the typical 4 year old answer, "I don't know." We then told him to go and lay on his bed and closed the door behind us. Neither of us knew how to respond. Jake is currently on a 'break' from friends right now. And $90 later and in two weeks he will have a new window.
If only he could get a job, I would make him pay for it!! KIDS!?!?!?