I have a feeling that they were flying along, fat dumb and happy, on autopilot,and bam, a generator fell off line, or some similiar electrical problem...autopilot disengaged and auto pressurization system went off line and drove all outflow valves to closed.
pilots woke up, ears hurt, hand flew for a few seconds and re engaged autopilot once electrics were sorted out and the manual, ac or dc control to manipulate the outflow valve was used.
while it is a non event for some...I'm sure the passengers felt it and got a bit scared