Ronald DeFeo Sr. was an American businessman known for his involvement in the DeFeo family and the tragic events that unfolded in their home in Amityville, New York. He was the father of Ronald DeFeo Jr., who infamously murdered his entire family in 1974. DeFeo Sr. was a car dealer and had a tumultuous relationship with his children, often described as strict and abusive. His family's story gained notoriety, leading to the infamous Amityville Horror case, which has been the subject of numerous books and films, further cementing the family's place in American true crime history.