During his robberies, Mason always operated with a partner (initially Wade, and later Turner). During the Burger Corral robbery, he and Wade beat, blindfolded, gagged, and restrained the night staff (all teenagers) right after closing hours (the males were tied up with their own belts and electrical wires, while the females were tied up with her own underwear), separated them by gender to establish dominance, raped the females, and killed them with single gunshot wounds to the head. He then took their valuables and the money from the register and the safe, then set fire to the restaurant and the victims' bodies as a forensic countermeasure. During the gas station robbery, Wade somehow shot the clerk with the same shotgun and intended to set fire to the gas station, but was arrested along with Mason before they could do so.
During the Dee's Original Diner robbery, Mason and his new partner Turner emulated Mason and Wade's Burger Corral robbery by restraining the night staff right after closing hours (using the same type of items, sorted by gender), raping Renee, and killing them with single gunshot wounds to the head fired by a handgun. They then stole the money from the register and the safe and set fire to the restaurant and the victims' bodies as a forensic countermeasure. They also took the victims' valuables.
There were some differences between the original murders Mason committed with Wade and the ones committed with Turner. In the Burger Corral robbery, all of the night staff were teenagers and were separated by gender to establish dominance. The males were found by the cash register and the females in the back office. Additionally, the victims were blindfolded before they were killed and the bodies were prone like they were shot while kneeling. In the Dee's Original Diner robbery, the victims were not all teenagers (José Rivera was eighteen, legally making him an adult). They also weren't separated or blindfolded, and were instead killed while facing each other, with the bodies being found within feet of each other. This distinction was a ritual aspect from Turner's personal M.O., meant a form of psychological torture. In line with that, José and Eddie were forced to watch them rape Renee.
During the robbery of the gas station, Turner shot the clerk in the neck while Mason shot out all of the security cameras as a forensic countermeasure, since they didn't have time to start a fire before the police arrived. Also, Mason spared a father and son who were in the store at the time while Lester wanted to kill them to avoid leaving witnesses. During the campground shootout with the BAU, Turner fired at Morgan, Reid, and a police officer with his semiautomatic handgun, while Mason made use of both his revolver and a shotgun.
The unsubs were initially believed to be the same individuals responsible for the Burger Corral murders six years ago. At the time, the BAU profiled that the murders were committed by someone with a personal connection to the town. However, it is a very transient place, with tourists and truckers and most of the job opportunities are seasonal. Based on the level of violence, there were two or more criminally experienced unsubs, likely under the influence of some type of narcotic. However, because they never struck again, the case went cold.
Since young staff are typically assigned to a night shift, the unsubs might have considered that as it would be easier to subdue a group of teenagers. Because the unsubs chose to strike in Las Vegas again, it is possible they could be sending a message to announce their return or it could be simply criminal ego: they had gotten away with killing before, so they decided to try it again at the same location. They may have been imprisoned in-between the original and new killings, which would account for both the dormancy and the criminal experience.
Based on Renee Acosta's voicemail, the unsubs are in a partnership and, because the M.O. in the most recent murders contained details that weren't released to the public, it was likely the same unsubs and not copycats. However, since there were also specific differences between the M.O.s in regards to psychological sadism and torture, there were two possible scenarios at hand: the unsubs were evolving, or only one was involved in the original murders and had since found a new partner. Regardless, the unsubs are still likely from the region and/or surrounding states and, since the crimes are impulsive and violent, are probably not that old, likely under the age of 45.
Following the unsubs' identifications, the BAU expanded their profile. A year after the Burger Corral murders, Mason was arrested along with Wade, his original partner, in Texas for a robbery-homicide. While incarcerated, they met Turner. After Mason and Turner were released, their new partnership was formed. It is believed that they returned to Las Vegas to emulate the original success that Mason had with Wade. They are methamphetamine users, so it is likely the limbic systems in their brains have been damaged. This is disconcerting, because it can dramatically alter behavior, and give rise to psychopathic tendencies, eventually evolving into an advanced psychosis. The dynamic between the unsubs is very rare, because it consists of two alpha males coexisting. They must have some kind of respect and/or fear that is keeping them together, but it is a tenuous bond. Eventually, a rift will grow between these two if it has not already.
Mason and Wade's 2009 robbery and mass murder at Burger Corral seems to have been inspired by a 1991 mass murder at a yogurt shop in Austin, Texas. In both cases, four teenagers were shot and killed inside a store that sold certain food, the girls were tied up with their own clothing and raped beforehand, and the store was set on fire afterwards as a forensic countermeasure. Multiple people were suspected in the 1991 case, with two suspects eventually being convicted and sentenced for the crime in 1999. However, the convictions were eventually overturned on the basis that their confessions were improperly used against each other. In 2009 (the same year the in-show Burger Corral killings took place), new DNA evidence found an unidentified man's DNA on at least one of the victims, which seemed to exonerate the two prime suspects, even though they knew details of the investigation that were never released to the public.
- William Duke Mason (deceased). Portrayed by Jesse Luken.
- Benjamin Wade (Mason's old partner; incarcerated). Portrayed by Blake Heron.
- Lester Turner (Mason's new partner; deceased). Portrayed by Stephen Monroe Taylor.
- The bikers are unique on Criminal Minds for being two distinct killing teams active years apart, with a mostly similar M.O. and a common member.