While The Amityville Horror films focus on the hauntings and dark spirits that exist in the house, what caused those paranormal symptoms was the mass murders that Ronald Joseph DeFeo Jr. committed against his family inside the house on November 13, 1974. At the time, DeFeo Jr. was just 23 years old.

The family's house was later said to be haunted and served as the inspiration for the Amityville Horror book and movies. On the evening of November 13, 1974, Ronald Butch  DeFeo Jr. entered an Amityville bar and told people his parents had been shot inside their home.