|“||Hey, you're pretty good.||”|
Living in a suburban area in Las Vegas, Gary was arrested in his youth for lewd behavior and also trespassing on the grounds of a nursery school. Later in life, he was again arrested when he exposed himself to a child. In 1984, Gary spotted a six-year-old boy named Riley Jenkins walking home alone from a T-ball game (due to his parents working late) and either offered him a lift to Riley's house or merely followed him to the residence. After somehow managing to get inside in the Jenkins house, Gary coaxed Riley into the basement, where he raped and killed him, leaving the body stuffed behind a washing machine. After murdering Riley, Gary began focusing on Spencer Reid, then another boy living in the neighborhood, ever since he watched his chess games in the park (even playing a round of the game with him at one point). Sensing something was wrong, Reid's mother Diana told Riley Jenkins's father, Lou, about her suspicions.
Two days after getting Diana's call, Lou, after looking into Gary's history and discovering his prior crimes, called Diana and had her lead him to Gary's house. Following Gary inside after spotting him taking out the trash, Lou confronted and beat him to death with an aluminum baseball bat. Discovering what Lou had done moments later, Diana slipped in and became soaked in Gary's blood, prompting her husband William (who had been told what had transpired and decided to help in covering it up, fearing Diana could be charged as an accessory to the murder) into burning them, an act which Reid witnessed. Lou disposed of Gary's body across state lines, burying it in the middle of the desert, where it was discovered by construction workers in 2001. Due to the body being in close proximity to the Barker Ranch, it was believed that it could belong to an unknown victim of the Manson Family, so DNA was taken and entered into the national database.
In 2008, while investigating child abductions in his hometown, Reid begins having nightmares about Riley Jenkins, which leads him to believe his father may have been the one who murdered him. Eventually, after reopening the case and investigating with help from Morgan and Rossi, Reid discovers Gary was the one who murdered Riley, with his mother and father (who he had managed to track down) telling him the rest.
Riley's killer was profiled as a white male aged in his late twenties to early thirties who likely knew Riley, meaning he may have been a neighbor. The crime was need-based and sexual in nature, so the perpetrator was a pedophile, while Riley's mouth being taped shut was symbolic; the unsub feared the boy would talk, panicked, weighed his options and killed him, thus making sure he'd never say another word.
Since Gary only killed one person, the term "M.O." is misused. After following Riley home or after finding some way to enter the house, he somehow coaxed the boy into the basement, where he raped him, taping his mouth shut either before or after doing so. The knife Gary stabbed Riley with was taken from the scene, being found by him among some fishing gear under the basement steps. As Gary watched Reid for some time, it is reasonable to assume he stalked Riley as well, to know when the perfect time to strike would be.
Gary's murder of Riley Jenkins seems similar to the murder of Danny Joe Eberle, the second victim of serial killer John Joubert. Both victims had their mouths taped shut and were stabbed exactly nine times.
- Unspecified date: Unnamed child (flashed only)
- Riley Jenkins (stalked for an unspecified amount of time; later raped, then stabbed nine times in the chest)
- Spencer Reid (intended to rape and presumably kill)