Classified as a paranoid schizophrenic by psychiatrists, David attributed his killings to demons who hounded him and would only be satisfied by the blood of women. Known from letters he sent to police as "The Son of Sam", he terrorized New York for two summers randomly shooting attractive women and their companions late at night. From prison, he later told a FBI investigator that he had made up the insanity story in case he got caught and in reality he was frustrated by his feelings in inadequacy with women. He admitted to stalked daily and shooting at random, revisiting the scene later to fantasize about the killing and masturbate.
Raised by adoptive parents in Bronx, David was big for his age and hyperactive but considered attractive and good at baseball. Devastated when his adoptive mother died of breast cancer, he believed that God wanted to destroy him and he introverted to a fantasy land.