(1) He wanted to be found guilty. I have a hard time imagining why, exactly, but I suppose another guilty verdict may have somehow boosted credibility in the gang he was supposedly associated with. (I also found it very odd when he got that neck tattoo. It's sort of like he expected and wanted to spend his life in prison and flaunted his guilt.)
(2) He felt guilty for getting away with those two murders (and/or perhaps other things he did).
(3) He realized that, despite this victory in court, he was unlikely to leave prison alive and couldn't bear to be away from his fiancee and daughter (or others).
I don't know. I was shocked when my wife told me he had been found dead. Maybe he was killed.