What psychological problem does Wilson Joel in Love liza have?

Wilson Joel 's wife in the movie love liza just committed suicide. Joel finds a letter from her but refuses to open it. He goes into a severe depression and starts inhaling gasoline. He starts having anger issues and hallucinations and eventually at the end doesn't even care if his house is burned down. He basically loses everything. what kind of psychological problem or using the DSM IV model, does he have? and why? what should i diagnosis him with and are there any suggested treatments or prognosis?