Matthew O'Brien first appeared in Bizarre Adventures #31 - Violence in a story written by Mark Gruenwald and drawn by Bill Sienkiewicz. He has not appeared since.
Matthew O'Brien was a film critic for the LA-based Cine Fantasy magazine, screening a film titled Gore Galore, which he considered to be "garbage." As the movie ended, the theater-goer seated behind him became upset that he did not have enough time to copy the credits. O'Brien, not recognizing the costumed man as being the Hangman, offered him his press kit, which contained information on the cast and crew.
Soon after, both the director and the producer of Gore Galore were found dead, and O'Brien immediately suspected the man from the theater. He attempted to alert the police, but was told that they were unable to commit manpower to follow up on his lead. O'Brien resolved to warn the other crew members himself, but had to do so in person because of the scathing criticism he had written about the film.
O'Brien arrived at the home of the screenwriter too late, discovering the wordsmith hanging from his ceiling. O'Brien then proceeded to a wrap party for Splatterday, a film which featured much of the cast of Gore Galore. O'Brien snuck into the party disguised as a delivery man, determined to warn the Hangman's potential victims.
All of the actors were in costume, making it difficult for O'Brien to discern who the Hangman's target would be. The critic's anxiety was further heightened when he discovered one of the party guests murdered. The Hangman grabbed another of the party-goers who was dressed in a cloak and hood, and throttled his victim to death. When he discovered that his victim was a woman, the Hangman was overcome with remorse over violating his personal code. As the villain agonized over this turn of events, O'Brien plunged the Hangman's scythe into the grief-stricken murderer's back, and left the scene in awe of how easy it had been to kill. His next review of a horror film talked about slasher films as cathartic exercise, offering praise instead of contempt.