Jason Michael Moss (February 3, 1975 – June 6, 2006) was an American attorney who specialized in criminal defense. He was best known as the author of The Last Victim: A True-Life Journey into the Mind of the Serial Killer (1999), a memoir about his exploration of the minds of incarcerated serial killers , which started as a research project in college. He corresponded and conducted personal interviews with several notorious killers.
Struggling with depression , Moss committed suicide in 2006. His book was adapted and produced as a film, Dear Mr. Gacy , released in 2010.
King was born September 21, 1947, in Portland, Maine. His father, Donald Edwin King, was born circa 1913 in Peru, Indiana , and was a merchant seaman. When Donald was born, his surname was Pollock, but as an adult, he used the surname King.    King's mother, Nellie Ruth (née Pillsbury; February 3, 1913 – December 28, 1973), was born in Scarborough, Maine.  Donald and Nellie were married July 23, 1939, in Cumberland County, Maine. 
As a child, King apparently witnessed one of his friends being struck and killed by a train, though he has no memory of the event. His family told him that after leaving home to play with the boy, King returned, speechless and seemingly in shock. Only later did the family learn of the friend's death. Some commentators have suggested that this event may have psychologically inspired some of King's darker works,  but King makes no mention of it in his memoir On Writing (2000).