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What Really Drove Criminal Minds Assassin Trevor Mills To A Life Of Crime

Over 15 seasons, "Criminal Minds" introduced viewers to a collection of kidnappers, torturers, and murderers unrivaled by any other series on network television. From a femme fatale assassin to a serial killer with a marionette fetish, the unknown subjects, or unsubs, the Behavioral Analysis Unit (BAU) profiled and pursued week after week were a disturbed and demented rogues' gallery that would even make residents of Gotham City gasp in shock.

In Season 7, Episode 15, "A Thin Line," the BAU goes to California to investigate the separate killings of two families in what appears to be a gang-related spike in crime. As the investigation advances, the team eventually realizes Trevor Mills (Kevin Sheridan) is one of two men behind the crimes, which had little to do with gangs. As the episode reveals, Mills is not just a serial killer, he's a family annihilator, a serial killer who targets and kills entire family households. Like many unsubs on the show, Mills experienced a violent trauma in his youth, which helped push him towards his murderous deeds.

A horrific trauma left Trevor broken and vulnerable

When Mills was around 15 years old, he and his family were victims of a brutal home invasion. The perpetrators, Ronnie Green and Carlos Jackson, broke into the Mills home, killing Trevor's father and sister. The pair beat and raped Trevor's mother, Pamela, who survived the attack but was left with severe brain damage. Trevor, who smartly hid in the closet while the assault occurred, was left to take care of his incapacitated mother and mourn the loss of his father and sister.

After news of the Mills tragedy spread, local businessman Clark Preston (Paul Johansson) took a keen interest in Trevor and his mother, even paying for Pamela's medical treatments. Trevor, broken by the attack, began to look upon Preston as a father figure. He began to parrot Preston's racist views. Trevor, though, is unaware that Preston was actually the mastermind behind the attack that destroyed his family. At the time, Preston was a real estate developer who needed a way to drive down the cost of the housing market so that he could buy and flip multiple properties. To accomplish that, Preston hired Ronnie Green and Carlos Jackson, and paid them to attack the Mills, in the hopes that Black perpetrators killing a white family would spark a race war, which would in turn lower home values in the area.

Trevor inflicted his own trauma on multiple families

"A Thin Line" begins 10 years after Green and Jackson's attack. Trevor, now in his mid 20s, has been largely brainwashed by Preston, who is currently running for mayor. With some manipulative prodding by Preston, Trevor comes to believe that the best way to ensure Preston's victory is to kill white families and blame the deaths on Black or Latinx innocents. He first targets the Mitchell family, killing all four members. Trevor frames a local gang member, Alex Collison, for the crime, killing him and leaving the Mitchells' gun with his body. Four days later, Trevor kills the Lewis family, and again frames and kills an innocent man of color. Two days after that, the Nelson family and Pedro Mendez meet the same fate.

A day after the Nelson family is killed, Trevor sets his sights on the Wilson family. Although Trevor succeeds in killing the family, Ramon Gomez, the man Trevor intended to kill and frame, manages to escape and reach the police. Eventually, the BAU unravels the history and connections between Trevor and Clark Preston. Though Preston is arrested, Trevor is shot and killed by the BAU while holding a woman hostage.

As the episode doesn't indicate that Trevor had any homicidal urges prior to the slaughter of his family, it can be assumed that the attack, and the subsequent influence of psychopath and father-figure Clark Preston, "created" the killer Trevor became.