I heard that Sonny/Billy was quite a character. He was nuts in real life and a lot of people were afraid of him.
Sonny was completely insane. He was the Haku of the talent for that movie. Almost 100% American Indian.
He was a cop in the great gang movie The Warriors. His big break was 48 Hours with Eddie Murphy. Played the crazy Indian that broke Ganz out of prison. Had a recognizable part in Poltergeist
No casting agents wanted to cast him because he was so volatile. shame, he had a great look and could actually act.