I would say most likely some PTSD from the Marines and a touch of schizophrenia. The "You talking to me scene" and the mohawk at the end shows signs of mental illness.
I liked the character. He seemed very right wing and wanted to clean the streets of the criminals and freaks. But he also had his own demons to deal with.

You talking to me?
Are you talking to me?
Who the fuck are you talking to?
Are you talking to me?