Robert K Ressler

Robert K. Ressler (1937-2013) was an FBI supervisory special agent and a reserve colonel in the United States Army. Before retiring, he served in the Army's Criminal Investigation Branch (CID). Afterwards, he worked as the director of Forensic Behavioral Services, a company that specializes in training, education, consultation, and expert witness testimony. He is the author of Whoever Fights Monsters and the basis for one of the key characters in Netflix's Mindhunter Original Series.