I personally don't think we need to speculate on whether he had 'legally labelled' mental illness or not. There are a great many people who have been pushed to the depths of despair in their life and who act out accordingly. Oompa appeared to have been unable to deal with the loss of his life as a JW and the absolute shunning by all of those he thought of as family and friends. This is not unfamiliar territory for most JW's who leave, especially those born in, raised in, married in....it isn't just walking away, it's the realization that nobody cares, that your life was an illusion, that you are trapped with the 'either or' scenario of going back or trying to exist outside - there are so many factors and so much destruction when most walk away. There are people I know that have 'left' physically years ago but who, once you talk to them, realize that they haven't left it all behind mentally or emotionally. The feeling of abandonment is a strong human emotion - and some people just have a harder time dealing with the pain.
He was who he was and had value in being himself. He was very clear about his demons - and those included his treatment of JW's including his parents and his wife. His value was tossed away by the very organization he had given much of his life too - sammieswife