Which seems to imply that the vehicle had automatic transmission, and an ineffective handbrake. Surely these type of vehicles should not be left unattended with the engine running... EVER...
phiggsbroadband,
You've probably never lived through a Canadian winter
It is quite common on winter mornings, to see cars running, with the doors locked, while the owner waits inside until it warms up. You can even buy remote starters, that allow you to start the car from inside your house!
As far as this incident is concerned, it is clear that after the driver moved the van forward a few feet, he forgot to put it in Park in his haste to get out and take over the shutting of the aircraft door.
The "handbrake" on this van, like most North American vehicles, is a foot-pedal, to the left of the brake pedal, with a ratchet to hold it on. It is referred to as the Emergency Brake, and is hardly ever used in normal driving. Most drivers, including me, rely on the Park setting of the transmission, unless on a steep hill.