Wow, that is sad and needless just because of some slight oversights from the rider and operator. The rider obviously didn't think the ride would toss him out and the operator probably didn't check or care to check if things were alright.
I can't believe that the ride is even able to operate while the safety harness is not buckled. Lousy design. Every time I have to design something. It has to be totally asshole proof, and fail safe. At 14, this kid seems quite oversized, and it doesn't look like the ride was designed to accommodate him. A simple continuity switch in the seat belt buckle thing would alert the ride operator that things are not alright and to check the passengers while preventing the operation in the ride via the controlling system. The way the ride goes, the over the shoulder harness was used to allow passengers to enter and exit quickly, but a shoulder harness like that is more for acceleration in the upward direction with relation to the passenger car. I assume this ride probably snaps up to requiring that restraint type also, but clearly from the video, it needs additional restraints for the downward passenger movement as the shoulder harness will have a tendency to open when high G forces are acting upon it, and just a simple seat buckle can cause someone to flatten a nut when the restraint is fasten correctly if the passenger is positioned just right. Even a simple foot plate may have helped in this case as an added passive restraint.