As a child, Ramirez sustained two serious head injuries. When he was two years old a dresser fell on top of him, causing a forehead laceration requiring 30 stitches to close. When he was five years old, he was knocked unconscious by a swing at a park, after which he experienced frequent epileptic seizures that persisted into his early teens. As a 12-year-old he was strongly influenced by his older cousin, Miguel ("Mike"), a decorated U.S. Army Green Beret combat veteran who often boasted of his gruesome exploits during the Vietnam War. He shared Polaroid photos of his victims, including Vietnamese women he had raped. In some of the photos Mike posed with the severed head of a woman he had abused.
Ramirez, or "Richie", as he was known to his family, was present on May 4, 1973, when his cousin Mike fatally shot his wife, Jessie, in the face with a .38 caliber revolver during a domestic argument. After the shooting Richie became sullen and withdrawn from his family and peers. Later that year, he moved in with his older sister, Ruth, and her husband, Roberto, an obsessive "peeping Tom" who took Richie along on his nocturnal exploits. Ramirez also began using LSD and cultivated an interest in Satanism.