The Last House on Dead End Street (1977)
Terry Hawkins, a drug dealer, is just out of prison. He decides to make a horror film with the help of two sadistic prostitutes, a porno cameraman, and a bestial pervert. His crew kidnap three people and graphically murder them in an abandoned warehouse. (IMDB Casey-52)
The film was made in 1972 and was initially unreleased until 1977 because one of its actresses sued over the use of hardcore loops Watkins shot of her. Watkins did not even know the film ever made its way to the big screen until late 1979, when someone on the street recognized him as "the guy from that movie that was throwing animal guts around".