I can't imagine how terrified this boy must have felt.
My husband had a similar situation in he and his nephew was seated in a roller coaster ride he was too short to go on. The attendant and his mom said he would be fine. The seatbelt didn't fit and his nephew was rising up out of the cart. My husband held on for dear life to his nephew. It terrified my husband while his nephew was oblivious and had a ball. I hate to think what may have happened if my husband wasn't paying attention.