It seems to me that this is another example of a pilot suicide. But, how could it have happened?
Has China Eastern not adopted the practice that when the cockpit door opens and a pilot leaves to go to the loo (or whatever), a Flight Attendant then takes the person's place?
How could the cockpit door be breached by a passenger? Those doors on modern planes were built to resist what seemed to have been done by some passengers on the flight that crashed in Pennsylvania in 2001.
There is more to this sad accident than we now know. And, I wonder, since it involved a Chinese airline, will we ever know what really happened?