The American murderer Ronald DeFeo -- whose 1974 killings of his parents and four siblings inside their home near New York inspired "The Amityville Horror" movie -- has died, prison officials said Monday.
DeFeo, who was serving a 25 years-to-life sentence at Sullivan Correctional Facility in northern New York state, died on Friday aged 69, the state prisons department said in a statement.
He was pronounced dead around 6:35 pm (2335 GMT) at Albany Medical Center, which is located around 150 kilometres (93 miles) from the jail, the statement added.
The cause of death was not immediately known and is pending a coroner's report.
The prison's department did not say whether DeFeo had been ill before he died. He was due for a parole hearing in July, according to prison authorities.
DeFeo was convicted of killing his mother, father, two brothers and two sisters on November 13, 1974 at their home in the coastal town of Amityville on Long Island about 40 miles from New York City.
DeFeo, who was only 23 years old at the time shot each of his parents twice and his siblings once. The victims were all found in their beds.
During the trial, DeFeo's lawyer unsuccessfully pleaded insanity for his client who claimed to be hearing voices.
The family massacre inspired the 1977 novel "The Amityville Horror, A True Story," which was the basis of the 1979 film "The Amityville Horror," which became a cult classic.
The movie was remade in 2005. In 2017, "Amityville: The Awakening:" became the latest dramatisation about the six murders.