[Cementjungle]

Did the engineer lock himself in and yell Allahu Akbar?

According to Fox, the engineer is refusing to talk to investigators. He's union of course, so naturally there will be a big fight over any disciplinary actions.

[Alberta's Child]

It has nothing to do with disciplinary action by the railroad. The crash site is being treated as a crime scene now.

It's a safe bet that human error is the one and only relevant contributing factor in this crash.