Bill Pattersonwas the FBI's chief profiler, and AgentFox Mulder's former mentor. He worked for three years investigating a series of grisly murders that culminated in the arrest of John Mostow, a Soviet emigrant. When the murders continued after Mostow's arrest, he requested that ADSkinner assign Mulder to the case.
Mulder found Patterson's partner, Agent Nemhauser's dismembered body in Mostow's sculpture studio. Mulder confronted Patterson and accused him of continuing the murders. Patterson attacked Mulder and fled the scene, only to be shot by Mulder on the rooftop. He recovered from the gunshot wound and was imprisoned.