Les Abend has been a commercial pilot for decades, he has written columns for FLYING magazine and is an Aviation Analyst for CNN. He, compared to most other analysts the media trots out, is "our guy on the inside", if you will. He is a Pilot, Captain, in fact. His input and opinions hold more water for me then an "outsider" or non-pilot.
Pilots are human too, we all know this. But at the same time, pilots are charged with the responsibility of making sure his or her passengers arrive safe at their destination. Pilots are held to a higher level, along with ship, rail, and bus crew members. All charged with passenger responsibility. If in fact, the First Officer deliberately caused this crash, it is obvious that there was something amiss with him and his mental state. It is in a pilots DNA to "fly the plane". I was watching CNN last night, and a reporter was at a training center with an A320 simulator. The instructor was showing the reporter what it might have looked like from the cockpit as the copilot flew the airplane into the French Alps. Seated in the right seat, he adjusted the altitude hold down to 100 ft, and increased the vertical speed downward. The "aircraft" raced towards the mountains. The GPWS started going off. The Master Caution began blaring. If one has never heard the Airbus Master Caution, if gets your attention, that is for sure. The reporters eyes were the size of fifty cent pieces as the computer-generated mountains wizzed by the windows. The instructor allowed the demonstration to get to a certain point and then he said something to the effect of "I can't do this, you know what? Let's get out of here." He disconnected the autopilot, pushed up the power, and pulled the nose up, silenced the Master Caution, and "flew the airplane" to safety.
My point is, even in a simulator, pilots are determined to not allow the aircraft to crash. It appears in this instance, the situation this pilot was dealing with was hidden from Lufthansa and Germanwings. I am sure he feared loosing his job. I am sure he loved flying. I am sure it was his passion. Lufthansa stated, other then a gap in his training record, he was a flawless pilot with a clean record. The leg down to Barcelona was uneventful. Maybe the Captain didn't have to piss on that leg. Maybe this was spur of the moment, or, maybe he had thought about it before and was waiting for the right time. When the Captain got up to use the restroom, he saw his chance, and locked the door. We may never truly know what was going on inside his head.
This is not the first time a pilot-suicide has ended the lives of the innocent:http://news.aviation-safety.net/2015/03/26/list-of-aircraft-accidents-and-incidents-deliberately-caused-by-pilots/
This is a "tour" of an A320 flight deck. At the 5:40 mark, she pushes the "TEST" button on the ENG #1 FIRE SYSTEM, it lights up and sounds the MASTER CAUTION:https://www.youtube.com/watch?v=kdQgGheK4KI
Also, at the 5:00 mark, the MASTER CAUTION is demonstrated and silenced via the button on the glareshield:https://www.youtube.com/watch?v=uqKeSO6msDk