I admit I know very little about the subway equipment, coming from a freight background upstate. But I don't understand was went wrong with the disabled train. Why does just pulling an emergency cord disable the train? After it comes to a stop, can't the emergency valves be closed or reset again to resume normal operation? And since they were able to move the train operating from the 6th car, the brakes must have been released on the head end. Sounds like the hoodlums did more than just pull a brake cord.
I was wondering that too.
That photo seems to shows x-over move.