So did they set the parking brake?

Just north of here, the Canadians suffered a dreadful train wreck.  Tank cars loaded with crude oil derailed in the center of town and burst into flames.  Five are known dead, 40 are missing, and it's a good bet the missing are actually dead, but the fire was so fierce nobody got close enough to check.  Center of town is burned out.
   The railroad (Canadian National? Canadian Pacific? the TV didn't bother to say) says that the train was parked, the crew was catching up on sleep in a motel.  It was claimed that "all safety devices were set". But somehow the train got loose and rolled into town.
There are a few questions unanswered.  Unasked by clueful newsies. 
Were the train brakes set, or just the engine brakes?  Every car in a train has air brakes as well as a separate set of brakes on the engine.  For ordinary operations (flat terrain, expected station stop) it's customary to use just the engine brakes.  Train brakes are reserved for tougher situations like decending mountain grades.  If the brakes on every car were set to park the train it is hard to understand how it could run away. If just the engine brakes were set, a run away is more likely.
   Brakes are fail safe.  Air pressure holds the brakes off.  Should the train line leak, or worse, separate, the air runs out and the brakes go on.  
   Were the diesel engines left running?  It's standard practice around here to leave them running, especially in winter, 'cause they might not start when cold.  A runaway is more likely if the diesels are running, with nobody on board.
   Oher interesting bit.  The train was loaded with North Dakota crude headed for an Irving refinery in New Brunswick.  Accident would not have happened if that North Dakota crude had been headed for a US gulf refinery thru the Keystone XL pipeline.