From April 1984 to August 1985, Ramirez murdered at least fourteen people during various break-ins, with his crimes usually taking place in the afternoon, leading to him being dubbed the Night Stalker, the Walk-In Killer, and the Valley Intruder.

Stone also stated that Ramirez was knocked unconscious and almost died on multiple occasions before he was six years old, and as a result "later developed temporal lobe epilepsy, aggressivity, and hypersexuality.

"[12] At age 12, Ramirez was taken under the wing of his older cousin, Miguel Angel "Mike" Valles (June 14, 1949 – April 8, 1995),[13] a soldier in the U.S. Army who himself had already become a serial killer and rapist during his service in the Vietnam War.

Mike often boasted of committing gruesome war crimes in Vietnam, and shared Polaroid photos with Ramirez showing Vietnamese women whom he had raped, murdered, and dismembered or decapitated.

[17] When he reached adolescence, Ramirez began to meld his burgeoning sexual fantasies with graphic violence, including forced bondage, murder, mutilation, and rape.

Although the husband beat Ramirez at the scene, criminal charges were dropped when the couple, who lived out of state, declined to return to Texas to testify against him.

[21] Like the graphic photos and stories of his cousin's war crimes in Vietnam, Ramirez would later similarly remark that witnessing the murder was not traumatic for him in any traditional sense, but rather a subject of fascination.

Mike was later found not guilty of Jesse's murder by reason of insanity, with the shooting attributed to post-traumatic stress disorder from his military service.

[24] After Mike was released from the mental hospital in 1977, he sometimes accompanied Ramirez and Roberto on these voyeuristic walks, spying on women in the nearby areas through their windows.

On April 10, 1984, Ramirez murdered Mei Leung, a nine-year-old Chinese-American girl, in the basement of her apartment building in the Tenderloin district of San Francisco.

Once they were in the basement, Ramirez beat, strangled and raped Leung before stabbing her to death with a switchblade, hanging her partially nude body from a pipe by her blouse.

[32][31] Nine months later, on March 17, 1985, Ramirez attacked 22-year-old Maria Hernandez outside her home in Rosemead, shooting her in the face with a .22 caliber handgun after she pulled into her garage.

[35] Within an hour of the Rosemead attack, Ramirez pulled 30-year-old Tsai-Lian "Veronica" Yu out of her car in Monterey Park, shot her twice with a .22 caliber handgun and fled.

The two murders, and an attempted third, in a single day attracted extensive coverage from news media, who dubbed the attacker, described as curly-haired with bulging eyes and wide-spaced, rotting teeth, the "Walk-In Killer" and the "Valley Intruder.

"[36] One week later, at approximately 2 a.m. on March 27, 1985, Ramirez entered a home that he had burglarized a year earlier just outside of Whittier and killed 64-year-old Vincent Charles Zazzara in his sleep with a gunshot to his head.

After beating the mortally wounded man into unconsciousness,[42] Ramirez entered Lillian's bedroom, bound her with thumbcuffs, then raped her after he had ransacked the home for valuables.

[43] Two weeks later, on May 29, Ramirez drove a stolen car to Monrovia and stopped at the house of Mabel "Ma" Bell, age 83, and her disabled sister, 81-year-old Florence "Nettie" Lang.

[50] On the night of July 2, 1985, Ramirez drove a stolen car to Arcadia and randomly selected the house of 75-year-old Mary Louise Cannon, a widowed grandmother.

[52] He stated that he was startled to see electrical sparks emanate from the cord, and when his victim began to breathe he fled the house believing that Jesus Christ had intervened to save her.

After quickly fencing the stolen items, Ramirez drove to Sun Valley, Los Angeles, and broke into the home of the Khovananth family.

[75] This leak infuriated detectives,[76] as they knew the killer would be following news coverage, which gave him the opportunity to destroy crucial forensic evidence.

[78] With his attack on the Romero residence aborted, Ramirez broke into the home of 30-year-old Bill Carns and his fiancée, 29-year-old Inez Erickson,[79] through a back door.

[78] The stolen Toyota was found abandoned on August 28 in Koreatown, Los Angeles, and police obtained a single fingerprint from the rear-view mirror despite Ramirez' careful efforts to wipe the car clean of his prints.

[89] The print was positively identified as belonging to Ramirez, who was described by police as a 25-year-old drifter from Texas, with a long rap sheet that included many arrests for traffic and illegal drug violations.

"[92] On August 30, 1985, Ramirez took a bus to Tucson, Arizona, to visit his brother, unaware that he had become the lead story in virtually every major newspaper and television news program across California.

[97] After noticing a group of elderly Hispanic women fearfully identifying him as "el matador," Ramirez saw his face on the front page of the newspaper La Opinión with a headline calling him "Invasor Nocturno" (English: "Night Invader")[95] and fled the store in a panic.

[97] After running across the Santa Ana Freeway,[98] he attempted to carjack an unlocked Ford Mustang but was pulled out by angry residents Faustino Pinon and Jose Burgoin.

A group of over ten residents (including Jose Burgoin's sons) formed and chased Ramirez down Hubbard Street in Boyle Heights.

"[100] On August 3, 1988, the Los Angeles Times reported that some jail employees overheard Ramirez planning to shoot the prosecutor with a gun, which he intended to have smuggled into the courtroom.

[111] On August 7, 2006, Ramirez's first round of state appeals ended unsuccessfully when the California Supreme Court upheld his convictions and death sentence.