At the middle of it all is 14-year-old Thomas "Tommy" Sullivan Jr., who took his own life in January 1988. He killed his mother, Betty Ann, set the family home on fire, and then slit his own throat.

The documentary series "Let the Devil In" debuted on MGM+ Sunday. The four-part series tells the story of Thomas Sullivan, who stabbed his mother Betty Ann to death before turning his own Boy Scouts ...