Kenneth Francis Harrison was born on September 4, 1938, in the Mission Hill neighborhood of Boston, Massachusetts. He was the son of Earl Harrison and Veronica Zemotel, who was born in Poland. Kenneth was one of two children in his family.

As a child, not much is recorded about his personal life or upbringing. After he finished the eighth grade, Kenneth struggled to find steady work. He became an unemployed itinerant cook, which means he moved from place to place without a permanent home. He lived in various rooming houses around the South End of Boston. Sometimes, he even stayed in South Station, which is a major train station in the city.

On April 15, 1967, six-year-old Lucy Palmarin disappeared while on an errand in Boston. Her parents reported her missing after she did not return home for dinner. Despite extensive searches, Lucy was not found until May 24. Teenagers discovered her body in the Fort Point Channel, and her death was initially ruled as accidental drowning.

On June 16, 1969, Joseph "Joe" Breen was at the Novelty Bar in Boston. After drinking, he left the bar with Kenneth Harrison. They got into a fight, during which Harrison killed Breen. Harrison later called the police, claiming he was the killer, and referred to himself as "The Giggler" before hanging up. Police found Breen's body in a pit the next day, and his death was ruled a homicide.

On November 27, 1969, the body of 75-year-old Clovis Parker was found in the same channel where Lucy was discovered. Her death was also ruled as accidental, despite the similarities to previous cases.

On December 26, 1969, nine-year-old Kenneth "Kenny" Martin left home to visit a friend. He encountered Harrison, who lured him to South Station. There, Harrison strangled Martin and hid his body under a canvas in a tunnel. Martin’s body was found ten days later.

Harrison was arrested on January 7, 1970, after tips led police to him. He was charged with Martin's murder and later with the murders of Lucy, Clovis, and Joe. During his trial, it was revealed that his sister had informed the police about his confessions.

Harrison was convicted of Martin's murder and sentenced to life in prison. Shortly after, he pled guilty to the other three murders. He intended to serve his sentence in a hospital, but this request was denied. He spent time at MCI-Walpole and was later transferred to Bridgewater State Hospital.

In April 1989, staff members found Harrison unresponsive in his room. He was taken to the hospital but later died from an overdose of medication. His death was ruled a suicide, and there were criticisms about the hospital’s handling of his case.