"Now wait. You think I killed them? No. No, no, no, I just bought their limbs."
Little is known about Cowles's early life, including why he became an acrotomophile in the first place. When he was younger, he was caught by his then-fiancée Sandy rubbing up against a mannequin with its leg missing, although she repressed the memory as she wanted to marry him. After marrying, the two eventually had a son named Corey together. Sometime afterwards, Cowles's marriage with Sandy deteriorated and she eventually divorced him. With him having custody over Corey, Cowles had to hide his acrotomophilic tendencies away from his personal life. Eventually, he was unable to control them anymore and purchased several human limbs from serial killer Steven Parkett, taken from Parkett's victims. He then began admiring the limbs in the safety of his personal storage room in the Cowles home. In order to preserve the limbs, however, he had to purchase a large amount of preservatives, which eventually attracted the attention of the BAU, who were investigating Parkett's killings.
Rossi and Kate approach him at his front door and ask to look at the preservatives. In response, he tells them to leave since they don't have a warrant and no probable cause to search the preservatives. However, this is a ruse from the BAU; he leaves the house with the limbs he purchased in a panic. Followed by the BAU, Cowles is arrested when he stops the car on an abandoned trail. Taken to an interrogation room, they learn of his acrotomophilic tendencies from him and Sandy. Rossi and Kate eventually learn from their conversation with him that he may be obsessed with limbs, but doesn't have the capacity for murder. They then learn from him that he received his limbs from an unknown source, which leads the BAU in Parkett's direction. What happened to Cowles afterwards was not specified, but considering that he purchased actual human limbs from Parkett (who was disposing them), he was most likely arrested for being an accessory.