IWannaKnow provided an excellent description of a possible scooter accident scenario from the 2nd floor hallway in the general threads #231, Thread 11:
The scooter scenario includes provides an answer for Rebecca's statement that he was not allowed to ride the scooter in the upstairs hallway as well as why for the scooter to be found on top of his shin.
It's heartbreaking however Max's accident happened.My heart goes out to his family.
I doubt JS would allow his son to do something unsafe. He was a good father by all accounts. And if we suppose that little Max was so misbehaved that he snuck a scooter into the home and hauled it all the way up the stairs, how in the world could he do that without RZ hearing him?
I'm sure the scene was staged and that the time it took to stage it was critical in getting the child oxygen, which he obviously didn't have.