Latest OFFICIAL news from Marseille French prosecutor, is that the Co Pilot took over the controls whilst the Pilot answered a call of nature, the door to the Cockpit was as is normal locked upon the Pilot leaving the Cockpit, the plane then started its descent.
The Pilot then attempted to re-enter the Cockpit but the Co Pilot would not open the door, the Pilot was knocking the door trying to open the door, this continued until the Plane crashed, the Co Pilot never uttered a word to the locked our Pilot, but they say that they could hear the Co pilot breathing, the Planes descent could only be done manually.

So whilst it was an accident, it was caused by a human action, and a deliberate action, the French Prosecutor is saying its Involuntary Homicide.