Gary Gene Grant was born on June 29, 1951, in Renton, Washington. He spent his childhood and teenage years living in poverty. His parents worked low-skilled jobs but struggled financially. They lived in a trailer park on the outskirts of the city. Gary's mother had a problem with alcohol, which led to many conflicts at home. He often witnessed his parents argue, which affected him deeply.

As a teenager, Gary faced a lot of mental stress. He lost interest in school and did not perform well in his studies. Eventually, he dropped out of school in the mid-1960s. Toward the end of the decade, he decided to join the Army. He was assigned to the Navy. However, during his initial time in service, he was bullied by other marines, which contributed to his mental health issues.

Gary did not complete his service in the military. He cited health problems as his reason for leaving and was dismissed just a few months after joining.

On the evening of December 15, 1969, Gary Gene Grant attacked 19-year-old Carol Adele Erickson. She was walking home from the library along a dirt road next to the Cedar River. During the attack, Grant stabbed her with a knife and then moved her body into nearby bushes. There, he engaged in necrophilia with her and also physically abused her corpse, causing lacerations on her neck.

In September 1970, Grant struck again. He attacked 17-year-old Joanne Mary Zulauf in broad daylight. He hit her on the head with a stone and took her into the woods. Once there, he raped and strangled her. Her body was discovered on September 22, just days later. A few days after this murder, Grant gave his girlfriend a wristwatch he had taken from Zulauf’s body as a birthday gift.

On April 20, 1971, Grant committed his final murders. He encountered two 6-year-old boys, Scott Andrews and Bradley Lyons, who were playing outside a house. He threatened them with a knife and led them into the woods about two kilometers away. There, he beat them and then killed them; he stabbed Andrews and strangled Lyons. After the boys were dead, he covered their bodies with leaves and branches. The bodies were found two days later.

Investigators quickly found a hunting knife with dried blood near the crime scene. The blood matched Scott Andrews’ type. The knife had the name "Tom Evenson" engraved on it. When Evenson was questioned, he said he sold it to Jerry Triplett, who then said he sold it to Jim Monger. Monger told police he had lent the knife to Gary Grant. Grant was arrested in his trailer on April 30, 1971.

During questioning, Grant could not provide an alibi for the day of the boys' murders. He first claimed amnesia but soon confessed to the killings while crying. The next day, with his father and lawyer present, he confessed to all four murders. His attorneys later tried to dismiss the charges, claiming illegal wiretapping had occurred during his confession. However, the court rejected this motion because his confession had been recorded legally.

Gary Grant’s trial began on August 12, 1971. Important evidence included the audio recording of his confession, the blood-stained knife, and shoe imprints that matched his shoes. Witnesses testified they had seen Grant near the crime scenes. His defense argued that he was insane and requested leniency, claiming he was a harmless person. A psychiatric exam found him sane, but noted he had impulsive behavior. After a short deliberation, the jury found him guilty of all counts. He received four life sentences without parole.

Since his conviction, Gary Grant has been held in various Washington State prisons. In 2020, he received renewed attention when an author published a book detailing his case. As of December 2020, he was still serving his sentence at the Monroe Correctional Complex.