I'll purely speculate on an unintentional emergency application (dynamiter?) somewhere on the tail of the train, set emergency on the rear propagating up, you hear the buff slack run out, the BOOM, over goes two empty spine flats in the middle of the curve, takes everything over with it.
You literally see that lead empty spine car jump vertically off the trucks.
Good thing it was moving so slow, lot of placarded tanks, and they were being super careful with whatever that trailing tank car was that stayed on the rails.
Watching Corman work real-time was an adventure. Those guys do not believe in 3-point protection, that's for sure.
