"Next time you tell your whores to keep their mouths shut."
McGregor became a Sheriff's Deputy at some point of his adult life. However, he was corrupt, and he came to found and lead a wide variety of criminal businesses that came to employ even his own colleagues in the Sheriff's office. His enterprises specialized in a variety of trafficking methods, such as humans, drugs, and arms. When he came to view the Sheriff as a potential threat to his activities, he had his Deputies attempt to orchestrate his death during a shootout, but that failed, and a Deputy was forced to fatally poison him instead. However, the entire conspiracy was witnessed by a group of prostitutes employed by Justin Mills, with whom McGregor offered a deal in exchange for his silence, as well as those from his prostitutes. In 2013, he and his Deputies began systematically torturing and killing Mills's prostitutes. They partially intended to silence them, one after another, but the murders were also part of a larger scheme to orchestrate the death of Peter Coleman, a former Texas Ranger who by that point had taken over the position of Sheriff.
Angels (Part 1)
"In Heaven or in Hell. Which one are you gonna go to, huh? You got anything you wanna get off your chest, 'cause the hour of reckoning is upon you, Preacher-man!"Unnamed and his true occupation unknown at the time, McGregor briefly appears in the beginning of the episode, killing Abigail Jones. He and other Deputies later kill Tabitha Ryerson and pose her body. Due to the killings, Mills begins to feel the heat and threatens a drug addict named Travis Henson into finding McGregor (in reality, Travis was an informant for McGregor and the other Deputies). When Travis does, McGregor instead offers him drugs in exchange for getting Mills to meet up at the local El Lobito's Diner. Travis does so and Mills takes the bait, to which McGregor murders Travis. Then, he kills two more of Mills's prostitutes and sets their bodies, alongside Travis's, in wait for Mills at the bar. When Mills discovers them, McGregor calls him and taunts him before saying that he left weapons for Mills to use against the police when they confront him, citing that they would never believe a pimp. Not knowing that the BAU discerned his innocence, Mills equips himself with the weapons and prepares to ambush them and Sheriff's Deputies as they arrive. However, McGregor fires first, hitting Coleman and tricking Deputies (as well as signaling his accomplices who are present) into firing at Mills, which in turn prompts him into firing back. After killing Coleman in order to further fuel the gunfight, McGregor then flees as Mills continues on firing, being briefly spotted by Blake and JJ.
Demons (Part 2)
"Knew I should've handled this myself!"
The shootout ends after Mills is forced out of the bar by Morgan and JJ and then shot and killed by the former. Reid, who was shot in the neck by Mills, witnesses McGregor escape the shootout before going to the hospital to recover. McGregor later orders Marty Bennett, Vicky Lorenzana, Greg Baylor, and the other corrupt Deputies to kill the BAU. He personally tries to kill Reid, but is cut off by Garcia, who heads into his room and shuts the door in his face, locking it. As a result, he orders Baylor to kill both of them. Later, when he approaches Bennett and Lorenzana, finding the both of them wounded after trying to kill Rossi and Blake, he murders them in a fit of rage. He then heads off to a junkyard he owns, where three of his colleagues are present. Hotch, JJ, and Morgan arrive at the junkyard and are engaged in a shootout. All three of his colleagues, plus another corrupt Deputy, are shot and killed by JJ and Morgan, while McGregor attacks Hotch and tries to shoot him with his gun, but is shot and killed by him in return.
"Oh Preacher, what have you gotten yourself into?..."
McGregor is never profiled by the BAU directly, as their profiles were more consistent to the ring of corrupt Deputies as a whole. However, he was deduced to be the strong leader of the ring due to his power and influence over the other Deputies, as well as his authoritative control over situations. Also, the original profile provided by the BAU of the ring (which assumed the unsub was working alone) was partially accurate to McGregor: he was a strong white male in his early 30s who was good with his hands and drove a large vehicle.
McGregor killed his victims by shooting them with either a .45-caliber M1911A1 (likely the same one he later supplied Mills with during the El Lobito's Diner shootout) or a 9mm Beretta 92FS pistol, usually execution-style. Before killing the prostitutes, he would use a ruse, which involved him performing consensual S&M on them, take them to an unspecified location and restrain them. His and the other Deputies' shared signature was carving knife wounds to the prostitutes' backs, the number and deepness increasing with each victim. In the case of Tabitha Ryerson, he shot her in the back of the neck before carving the knife wounds to her back, not after. He then washed her legs in lavender (as a reference to spikenard, which is mentioned in the Gospel as the ointment used for Jesus's feet) and then posed her body. This deviation in M.O. was meant to convince the BAU that Tabitha's murder was more religion-oriented than the previous ones and therefore lead to suspicion being placed on Mills.
McGregor may have been partially inspired by Gerard Schaefer, a double murderer, suspected serial killer, and possible necrophiliac, who also worked as a Sheriff's Deputy. McGregor also has some similarities to Robert Lee Yates, a serial killer who also worked in law enforcement and had the same M.O. of targeting prostitutes, soliciting sex from their victims as a ruse, and shooting them once in the head.
- Until Demons, McGregor is the fourth unsub in the show's history to not have his name revealed by the end of the episode, despite being credited by said name. The first is Billy Flynn, whose name wasn't revealed at the end of his debut episode Our Darkest Hour even though he was credited by it (although his name was then revealed in the episode's follow-up The Longest Night). The second is Steve, whose name was never disclosed in Sense Memory, the episode he appeared in. The third is John Nichols, whose name was never disclosed in The Black Queen, the episode he appeared in.
- ↑ It is erroneously stated in "Demons" that Wagner was killed on the same day as the unnamed Sheriff when "Angels" placed the date of Wagner's death at June 21