So far this guys union reps said the engineer was possibly fatigued from working too many hours.
Others have suggested projectile into the windshield knocked out the driver and caused the train to accelerate.
A poster last night suggested a passenger terrorist snuck up behind the engineer and knocked him unconscious, jammed the throttle fully on, and then ran back to his seat.
There no way for a passenger or anyone to get inside the engineer while it’s in motion.
There are no doors or entry way into the engine from the passenger section of the train.
The only way for anyone to have gotten onto the engine was at the station or leaped onto the engine while going slow in the yards outside the train station.