That or something between incompetence and gross negligence.
Maybe someone needs to reevaluate the protocols for leaving a train loaded with crude oil unattended at the top of a grade.
We have a winner!!!
Insight: How a train ran away and devastated a Canadian town
http://www.freerepublic.com/focus/f-news/3040657/posts
Be sure to read post #27 as part of the understanding why the breaks eventually would fail after shutting down the air supply. Not immediately, they would first hold close but still depends on individual pressure tanks to hold the breaks after loss of main supply.