Pure evil if that is what they did. How did they know the plane would not break apart when it hit 45,000 ft or that their oxygen would work on themselves.
This is just 2000 feet above the plane's service ceiling, no way it would break up. Their oxygen tanks would work as they had prepared for this well in advance and knew what they were doing.
This plane is in the hands of Al Qaeda right now being outfitted with either a Paki nuke or packed to the gills with conventional explosives. The bang from this is going to make 9/11 look like a firecracker.