|“||We've got a few more holes to dig.||”|
— Jason to Ellen Russell and Darlene Beckett
Little is revealed about Nelson's early life or how he became a psychopath and a pedophile. Sometime in his adulthood, he started his series of rapes and murders, claiming the lives of at least four girls, including one Kelly Taylor, whose disappearance on March was pinned on Mark Logan, one of three friends who were with him at the time of the murder; Mark actually participated in sexually assaulting her, while the other two apparently watched them. After murdering Kelly, apparently without the knowledge of his friends, Nelson then disposed of her body. Mark took the fall for Kelly's disappearance and was sentenced to ten years in prison (since her body was never actually found at the time), which was spent being visited by Nelson and his other friends.
After killing both Mark Logan and Paul Montgomery, two of the other men who were involved in Kelly's murder, Ellen Russell and Darlene Beckett (the latter of whom was Kelly's mother), break into Nelson's apartment in the middle of the night and confront him. Feigning remorse, Nelson offers to take them to where Kelly's body is buried in exchange for his life. As the three of them drive to the burial site in Ellen's SUV, Nelson reveals his true nature as he tells the women how Kelly suffered in detail, then reveals that he had been expecting someone to come for him ever since Mark and Paul were killed, and told his neighbor to write down the license plate numbers of any strange cars that showed up outside his place and report them to the police. Angered by his deception, Ellen pulls over and throws Nelson out onto the pavement, intending to kill him, but is stopped by Darlene, who wants to find Kelly's body so she can have closure. Meanwhile, the BAU arrive at Nelson's apartment and find his trophy collection while searching for evidence. Reasoning that he would have moved Kelly's body after finding out his accomplices are dead, they examine Nelson's on-site storage unit and find a recently-used shovel. After the field agents identify the type of soil on the shovel's blade, an uncommon type for the area, Garcia is able to determine the location where Nelson had most likely reburied the remains.
Sometime later, Nelson tells Ellen to pull over again. When they all get out of the car, he tells the women that he has decided that he won't take them to Kelly's burial site unless they kill a random person, explaining he wants Ellen and Darlene to know how he felt the day he decided to kill Kelly and reminding them that the longer their trip takes, the better chance the police has of finding them. Against Darlene's objections, Ellen opens fire on a passing motorist, causing his truck to careen off the road and down a nearby hill. As the group continues on to Kelly's burial site, Nelson taunts Ellen, accusing her of secretly enjoying shooting at a stranger for no reason. He also tells her that they should team up and start killing across the country. Ellen responds by threatening Nelson, saying that she will kill him if he doesn't lead them to Kelly's body soon. He eventually leads them to an open field at the base of a hill just off the road, claiming that he isn't sure exactly where Kelly's body is since he had moved it after his friends were killed. When he finally finds the right spot, Ellen hands him a shovel and orders him to start digging. Eventually, Nelson unearths Kelly's skull. When Darlene asks him where the rest of Kelly's remains are, he tells her he had dismembered her body and buried it in different places all over the field, and says they will have a few more holes to dig to find the rest of her. Enraged, Darlene attacks Nelson, bludgeoning him to death with the shovel before she and Ellen flee the scene. Nelson's body is later found by Rossi when the BAU arrive at the burial site.
Nelson targeted young girls, attacking them when they were isolated and raping them before killing them. Because the bodies weren't found until the end of the episode, it is never revealed exactly how he killed his victims, but since Nelson alleged to have dismembered Kelly Taylor's body, it is possible they died this way. After killing them, he took jewelry or small articles of clothing as a trophy.
No official profile was made for Nelson, as the BAU were more focused on Ellen and Darlene. However, when examining evidence found at his apartment, they concluded that he was a clinical psychopath, incapable of feeling empathy, but being able to fake it in order to blend in or buy him time.
Elements of Kelly's murder, especially the method of disposal of her body and its subsequent discovery, seem to be similar to the murder of Jon-Niece Jones.
- Unspecified dates: At least three unnamed girls
- March 2002: Kelly Taylor
- October 10, 2012: Unnamed male motorist (attempted, but barely survived; manipulated Ellen into shooting him)