The plane had a history of decompression issues, additionally, the plane circled in autopilot around its last waypoint for a few hours, the landing was scheduled for 10:45, and it crashed around 12:20, it sounds like it ran out of fuel.
It could have been a faulty crew oxygen system in the cockpit. The passengers froze to death. Pretty terrible way to go.
There was a text message from a passenger as well. No mention of terrorists, just that the pilots were passed out.