Six replies already, and no one has posted a Google map of the descent path or METARS for the Seattle region at the time of the incident. Tut!!
The questions that need to be asked are 1) Was it a CFIT? ie. was the door under control at the time of impact. 2) Have the "Black Boxes" been located, that's providing the door in question had it's own and 3) Can't think of another. I am sure there must be more.