Copycat Killers: Mark Twitchell and 6 More Murderers Who Duplicated Crimes

Some killers have borrowed the names, symbols and methods of notorious murderers who came before them. Others have drawn inspiration from horror movies, television shows, novels or even characters created on the internet. These crimes are often described as “copycat” killings, although exactly what qualifies—and how much the original source influenced the violence—can be difficult to determine.

In the clearest cases, the imitation is deliberate. New York killer Heriberto “Eddie” Seda, for example, modeled himself after California’s Zodiac Killer, adopting his symbols and targeting victims according to their astrological signs. Other cases involve a looser mix of fascination, imitation and fantasy.

However, inspiration is not the same as cause. Researchers who study copycat crime caution that media exposure may give an already troubled or motivated offender ideas about how to commit a crime without creating the desire to kill in the first place.

Beginning in 1990, New York City was confronted by a series of shootings accompanied by cryptic messages that immediately recalled one of America’s most infamous unsolved cases. The original Zodiac Killer had terrorized Northern California in the late 1960s, killing at least five people and taunting police and newspapers with letters, symbols and coded messages.

The New York attacker similarly sent letters to authorities and the media, used a version of the Zodiac symbol and claimed to choose victims according to their astrological signs. Police initially considered whether the original Zodiac could have resurfaced on the opposite side of the country, but differences in handwriting and descriptions of the gunman pointed toward a copycat. The killer was eventually identified as Brooklyn resident Heriberto “Eddie” Seda, who had become fascinated by the original Zodiac case. Between 1990 and 1993, Seda attacked multiple people, killing three.

Seda was caught almost by accident in 1996 after shooting his half-sister during a domestic confrontation and engaging police in a lengthy standoff. A detective noticed similarities between Seda’s handwriting and symbols and those used by the New York Zodiac. Investigators ultimately connected him to the earlier attacks. In 1998, Seda went through two trials and was sentenced to 83 years in prison in one trial and 152 years in the second.

In 2008, aspiring Canadian filmmaker Mark Twitchell rented a garage in Edmonton, Alberta, and used a fake online dating profile to lure men there by pretending to be a woman. His first known target was Gilles Tetreault, who arrived expecting a date but instead encountered a masked attacker. Tetreault managed to fight back and escape.

About a week later, 38-year-old Johnny Altinger was lured to the same garage under similar circumstances. This time, the victim disappeared. Twitchell gained access to Altinger’s email account and sent messages to his friends claiming that Altinger had suddenly left on an extended vacation. Police investigating his disappearance eventually traced him to Twitchell and the rented garage.

What investigators found on Twitchell’s computer helped reveal just how extensively he had contemplated murder. He had written a document called SK Confessions, presented as the story of a man becoming a serial killer. The narrator described using a fake dating profile to lure a man to a garage and attack him, followed by another encounter in which he killed and dismembered a victim. The similarities to the attacks on Tetreault and Altinger were so specific that prosecutors argued the supposed work of fiction was actually a thinly disguised account of Twitchell’s crimes.

Twitchell was also fascinated by the television series Dexter, whose title character leads a secret life as a serial killer. Twitchell reportedly wrote online that he had “way too much in common with Dexter Morgan,” and even set up a “kill room” in his garage similar to one used by the fictional killer, leading the media to dub him the “Dexter Killer.” 

However, the connection was never as simple as Twitchell merely copying a television murder. His own writings, fake dating profiles and repeated attempts to lure victims showed that he had developed and carried out an elaborate plan of his own. In 2011, Twitchell was convicted of first-degree murder in Altinger’s death and sentenced to life in prison. 

Idaho teenagers Brian Draper and Torey Adamcik shared an interest in horror movies and filmmaking, but their fascination with violence extended beyond fiction. They were particularly drawn to Scream, the 1996 slasher film whose teenage killers turn murder into a kind of real-life horror movie. Draper was also fascinated by the 1999 Columbine High School massacre, and the teenagers discussed notorious killers and the possibility of committing crimes that would bring them similar notoriety.

By September 2006, their fantasies had developed into a plan. Draper and Adamcik created a “death list” of potential victims and recorded themselves talking about becoming killers. On September 22, they visited 16-year-old classmate Cassie Jo Stoddart, who was housesitting for relatives near Pocatello, along with Stoddart’s boyfriend. Draper secretly unlocked a basement door before he and Adamcik pretended to leave. They then changed into dark clothing and masks similar to those worn by Scream killer Ghostface, returned through the basement and began switching the house’s power on and off in an effort to frighten Stoddart and lure her downstairs. After her boyfriend left, they attacked Stoddart, stabbing her 29 times.

The teenagers had documented much of their planning on videotape. In footage recovered by investigators, they discussed Stoddart as one of their intended victims, talked about killing other classmates and imagined the notoriety their crimes might bring them. Their references ranged from Scream to real-life murderers, and evidence presented at trial also revealed Draper’s preoccupation with Columbine. Both were convicted of first-degree murder in 2007 and sentenced to life without parole. 

Unlike most supposed copycat killers, Morgan Geyser and Anissa Weier were not inspired by a real murderer—or even a character from a popular movie or book. Their fixation centered on Slender Man, a faceless supernatural figure created online in 2009 that quickly spread through horror stories, artwork and videos.

By 2014, the two 12-year-old Wisconsin girls had become deeply immersed in Slender Man mythology. Geyser believed the character was real, and Weier became convinced through her friendship with Geyser. Together, they began discussing killing someone to prove their loyalty to Slender Man, become his “proxies” and protect themselves and their families from him.

On May 31, 2014, after a sleepover, the girls lured their 12-year-old friend Payton Leutner into woods near Waukesha, Wis. Geyser stabbed her 19 times while Weier encouraged the attack, and the pair left her behind and set off on foot, reportedly intending to reach a forest where they believed Slender Man lived. Leutner managed to crawl to a bicycle path, where a passing cyclist found her, and survived.

Police apprehended Geyser and Weier several hours later. Their beliefs about Slender Man and their mental health became central to the legal proceedings. Geyser, who was diagnosed with schizophrenia, was found not guilty by reason of mental disease or defect and committed to a psychiatric institution for up to 40 years. 

Weier and Geyser were both charged with first-degree attempted homicide. Weier agreed to a plea deal with prosecutors that lessened her charge to second-degree intentional homicide, acknowledging her role in the murder. She was subsequently found not guilty by reason of mental disease or defect and committed for up to 25 years.

The case became one of the most notorious crimes associated with internet culture, but it was not a conventional copycat attack. There was no Slender Man murder for the girls to imitate. Instead, an invented online mythology became incorporated into their beliefs until they saw committing a real murder as a way to enter that fictional world.

On February 2, 1996, 14-year-old Barry Loukaitis entered his algebra classroom at Frontier Junior High School in Moses Lake, Wash., carrying a rifle and two handguns. He killed classmates Arnold Fritz and Manuel Vela Jr. and teacher Leona Caires, wounded another student and held the remaining students at gunpoint before P.E. teacher Jon Lane overpowered him.

Investigators soon uncovered Loukaitis’s fascination with violent books and movies. Among 28 Stephen King books in his bedroom was Rage, published under the pseudonym Richard Bachman, which was found on his nightstand. The novel follows a troubled teenager who brings a gun to school, kills teachers and holds his algebra class hostage. 

Friends also described Loukaitis’s interest in Natural Born Killers, the 1994 film about a murderous couple who become media celebrities. Prosecutors argued that Loukaitis had drawn ideas for his carefully planned attack from both.

Loukaitis had reportedly been bullied at school and had specifically talked about wanting to kill Vela, while his family was going through a bitter breakup amid his parents’ divorce. His attorneys argued that he suffered from serious mental illness and even showed jurors Pearl Jam’s “Jeremy” music video, about a troubled and alienated student, as they sought to explain the influences on his deteriorating mental state. The jury rejected his insanity defense and convicted him of murder and other crimes in 1997.

The case also had an unusual aftermath. After Rage was connected to several incidents of school violence, King asked his publisher to withdraw it from publication. He later said he did not believe his novel had caused the attacks but worried it could act as an “accelerant” for troubled young people already contemplating violence.