Marc DeFeo wurde am 4 September 1962 in Brooklyn, New York City, New York, USA geboren. Er starb am 13 November 1974 in Amityville, Long Island, New York, USA.
Was shot with a 35 caliber lever action Marlin 336C rifle by his older brother, Ronald DeFeo. Marc and his brother, John are fired at close range (less than 2 inches). The bullets penetrated the heart, lungs, diaphragm and liver of each victim. The spinal cord of John is severely affected.
