I also was in a similar situation. Not as bad as the engineer in discussion but, I went through similar situation.
Years ago, I started getting signals that my work was preparing to let me go, like putting me on Performance Enhancement Program, etc etc. The thing is I had not kept up with my skills and so I really couldn't find any work with similar pay I could switch to. I also decided to stay to do better work in order to prove the managers wrong. I wanted to prove the management wrong, that I'm someone worthy of employment. I wanted to prove to them that I am a person, not some disposable tool to be tossed aside. I now know it was a mistake.
The stress at work kept building up in me for weeks. I woke up in middle of nights, and I am someone who sleeps like a brick.
And it hit me. One morning, as I was stuck in a stop-and-go traffic on way to work on freeway, I went over the little section of freeway that allows you a full view of the long lines of cars packing the freeway. This view suddenly caused me panic attack and I began to feel claustrophobic. I felt the urge to take off my socks (and strip off shirt, which I didn't) and open the window (which I did) so that I could relieve the feeling of trapped in the car. I had never felt such sensation before. I believe the issue of claustrophobia went on for about 2 years, as I remember worrying about taking a flight to visit family.
I never never had such issues before.
I think I can understand why the engineer didn't leave for another job. With his experience, he could've have gotten another similar or better job, but I believe he wanted to prove the management wrong. But unfortunately the stress got to him first.