In “Psycho Killer,” David Scott interviews a man who calls himself the oldest serial killer in America, Gary Michael Hilton. In his first-ever televised interview, the so-called “National Forest Serial Killer,” confesses for the first time to the murder of a Florida woman, and reveals new information about three other homicides. Throughout the harrowing and chilling episode, Scott gets Hilton to open up about his killing spree, including how he chose his victims as he preyed on hikers in North Carolina, Georgia, and Florida.