Marty Chonks is the owner of the Bitch'n' Dog Food Factory in Portland. During the game's story, his business runs into financial burden as his wife makes extravagant purchases and a shyster bank manager has dramatically increased interest rates on his loan payments. To get his business back afloat, Chonks relies on criminal activity, including murder and insurance fraud.
All of Chonks' missions involve Claude picking up those involved in the economic decline, and taking them to the dog food factory where they are lured inside the building and murdered by Marty. In order, his missions are The Crook, targeting the manipulative bank manager, The Thieves, targeting the two thieves involved in Chonks' insurance fraud scheme, and The Wife, where the target is Chonks' own wife. In his final mission, Her Lover, Claude delivers a man named Carl, who was having an affair with Mrs. Chonks. At the end of the mission, Carl reveals a shotgun and shoots Chonks, before being killed by Claude himself.
Marty Chonks is considered a myth in the game because of his actions as a serial killer. In fact, his model is taken directly from the rumored Serial Killer pedestrian, albeit with a different head. It's possible that Marty's appearance was the impetus for the theories about the killer pedestrian. At times, the pedestrian can confuse players and make them think that Chonks is walking the street, either surviving his assassination attempt or committing murders outside of his missions, but these are just simple misidentifications.