Infamous "Amityville Horror" killer Ronald DeFeo died in a New York hospital last week of unknown causes at the age of 69.
State department of corrections officials confirmed his death on Monday, first reported by Newsday.
DeFeo died at Albany Medical Center on Friday; his cause of death will be determined by the county medical examiner's office.
The former Amityville man was serving out a prison sentence at Sullivan Correctional Facility for the murders of six family members in 1974.
DeFeo was 23 years old when he shot his parents, two sisters and two brothers while they were sleeping in their Amityville home.
The Long Island home was later made famous in the 1979 film "The Amityville Horror."