In October 2008, an aspiring Edmonton filmmaker built a real-life “kill room” modeled on a television serial killer — then used it twice. One man escaped. One man didn’t. This is the full story of Mark Twitchell, the case that became known across Canada and internationally as the “Dexter Killer” murder.
Who Is Mark Twitchell?
Mark Andrew Twitchell was born July 4, 1979, in Edmonton, Alberta. He attended the Northern Alberta Institute of Technology (NAIT), studying radio and television arts, and by his mid-20s had built an identity around independent filmmaking — much of it centered on his lifelong love of Star Wars. He helped organize fan events, produced a Star Wars fan film called Secrets of the Rebellion, and was known among friends and classmates as intelligent, articulate, and deeply immersed in fandom culture.
His personal license plate read “DRK JEDI.” A former classmate later described him as “a good guy, but untrustworthy” — someone who didn’t lie because he lacked principles, but because avoiding consequences mattered more to him than the truth.
Twitchell’s first marriage, to an American woman named Megan, ended in divorce in 2004 after the couple lived in Peoria, Illinois. Court filings from that divorce cited “extreme and repeated mental cruelty” and described Twitchell’s compulsive buying and reselling of Star Wars memorabilia. He returned to Edmonton afterward, remarried, and had a daughter in 2007. By 2008, his second marriage was also unraveling — he and his wife, Jess, were living largely separate lives inside the same house.
Around this same period, Twitchell became fixated on the Showtime series Dexter, about a forensic blood-spatter analyst who moonlights as a vigilante serial killer. He began identifying with the character directly, at one point updating his Facebook status to read: “Mark has way too much in common with Dexter Morgan.”
The Rehearsal: House of Cards
In the summer of 2008, Twitchell rented a detached garage in Edmonton’s Mill Woods neighbourhood and used it to shoot a short horror film called House of Cards. The plot follows a man lured from an internet dating site to a remote garage, where he’s tied to a chair and killed by a masked attacker.
Weeks later, prosecutors would argue, Twitchell used that same garage — and strikingly similar methods — on two real victims.
The First Attack: Gilles Tetreault
On October 3, 2008, Gilles Tetreault, a 33-year-old Edmonton man, believed he was meeting a woman named “Sheena,” whom he’d connected with on the dating site PlentyOfFish. Sheena’s profile described her as new to the city, recently relocated from British Columbia. She gave Tetreault unusual instructions: rather than a front-door address, he was told to enter through a detached garage and walk across a backyard to reach her basement apartment.
Tetreault followed the instructions. Inside the garage, he was attacked by a man in a black-and-gold hockey mask, armed with a stun baton and what turned out to be a plastic replica handgun. A prolonged struggle followed — Tetreault managed to escape, fleeing into an adjacent alley, where a couple walking their dog witnessed the confrontation. His attacker, momentarily caught off guard by the presence of witnesses, called after him using a fabricated name — “Frank” — before retreating.
Tetreault didn’t report the attack to police right away. Ashamed and shaken, he told only a few close friends and family members over the following weeks, though several urged him to go to authorities. He would later write about the incident in his self-published memoir, The One Who Got Away: Escape from the Kill Room.
The Second Attack: Johnny Altinger
One week later, on October 10, 2008, 38-year-old Johnny Altinger — a quality control worker, motorcycle enthusiast, and longtime user of online dating sites — believed he was meeting a woman named “Jen,” whom he’d met on PlentyOfFish. He was led to the exact same garage.
Altinger never returned home.
Days later, friends began receiving emails from his account claiming he’d fallen for “an extraordinary woman” and impulsively left for a vacation in Costa Rica. The emails struck close friends as immediately suspicious — the tone and phrasing didn’t sound like him. When they checked his apartment, they found his passport, toiletries, and other essentials for international travel still there.
Altinger was reported missing on October 16, 2008. His mother, Elfriede, learned of the supposed Costa Rica trip while she herself was traveling and grew increasingly alarmed as her son remained unreachable.
The Investigation
Police traced Altinger’s last known movements to the rented garage in Mill Woods, and from there, to Mark Twitchell. Twitchell was initially cooperative, even offering to show investigators the garage himself — but by the time they arrived, the locks had been changed and the space cleared out.
Detectives also discovered that Altinger’s car had come into Twitchell’s possession; Twitchell claimed he’d purchased it for $40 from a stranger who said he was leaving the country with a wealthy new girlfriend.
On October 20, 2008, Twitchell sat for a lengthy police interview with Detective Bill Clark. For the first two hours, he was calm and cooperative. When Clark directly accused him of involvement in Altinger’s disappearance, Twitchell’s demeanor shifted — though he never confessed. At one point, when Clark told him he wouldn’t be able to live with himself, Twitchell replied: “You’d be surprised what I can live with.”
He was arrested on Halloween, October 31, 2008, and charged with first-degree murder. Investigators had by then recovered a deleted document from his laptop — later dubbed “SKConfessions” — describing, in detailed first-person narrative, a plan to lure and kill men using fake online dating profiles.
News of the arrest reached Gilles Tetreault on November 2, 2008, when a friend directed him to a news article describing the case. Recognizing the hockey mask and the garage from his own attack, Tetreault came forward to police, and Twitchell was subsequently also charged with the attempted murder of Tetreault.
SKConfessions and the Trial
Twitchell’s trial began in March 2011 and lasted approximately three weeks, involving 72 potential witnesses. The Crown’s case centered heavily on the 42-page “SKConfessions” document, which opened with the line: “This story is based on true events. The names and events were altered slightly to protect the guilty. This is the story of my progression into becoming a serial killer.”
The document described, in graphic detail, both attacks — the failed attempt on a man given the pseudonym “Jim,” and the successful killing and dismemberment of a second victim. Twitchell’s defence argued the document was a work of fiction, “based on” real events in the loose sense a novelist might use the phrase, and that he had killed Altinger in self-defence after a staged movie-publicity stunt went wrong.
Twitchell testified in his own defence, admitting he had killed Altinger but describing himself as “frozen by inaction” in the moment, weighing whether to call for help against how the situation “would look.” Under cross-examination, prosecutors walked him through an extensive pattern of documented lies — to his wife, his friends, police, and both of his victims — undermining his self-defence narrative.
Forensic evidence played a significant role: luminol testing revealed 222 separate blood-impact stains inside the garage, along with blood in the trunks of both Twitchell’s car and Altinger’s. Investigators recovered seven blood-stained knives, a pipe, handcuffs, and hand-drawn sketches labeled “victim chair” and “killer chair.”
Nearly twenty months after the murder, Twitchell voluntarily handed police a hand-drawn map leading to a sewer near his parents’ home, where partial skeletal remains were recovered in June 2010. A forensic pathologist testified that the dismemberment methods described in SKConfessions were medically consistent with the condition of the remains recovered.
Verdict and Sentencing
On April 12, 2011, after roughly five hours of deliberation, a jury convicted Mark Twitchell of first-degree murder in the death of Johnny Altinger. He was sentenced to life in prison, with no possibility of parole for 25 years. A separate attempted murder charge related to the attack on Gilles Tetreault was formally stayed by the Crown in June 2011, since a conviction would not have added to his existing sentence.
Twitchell filed an appeal of his conviction, partly citing what he described as sensationalized media coverage. He withdrew the appeal in 2013.
Life After Conviction
Twitchell has remained a subject of public fascination in the years since his conviction. He has attempted to sell artwork and celebrity sketches from prison, launched an online blog through an intermediary, and repeatedly sought the return of unreleased film footage seized by police during the investigation. Edmonton police have consistently declined these requests.
The case inspired journalist Steve Lillebuen’s book The Devil’s Cinema: The Untold Story Behind Mark Twitchell’s Kill Room, which won Canada’s Arthur Ellis Award for best nonfiction crime writing. Gilles Tetreault later published his own account, The One Who Got Away: Escape from the Kill Room.
Actor Michael C. Hall, who portrayed Dexter Morgan on the Showtime series, addressed the case publicly in 2012, calling it “horrifying” to consider that his character may have influenced a real murder.
Where the Case Stands Today
Mark Twitchell remains incarcerated at a maximum-security facility in Saskatchewan and will not be eligible for parole until 2033. Johnny Altinger’s remains were never fully recovered — his skull and several other remains were never located. Gilles Tetreault has spoken publicly about the case in the years since, including in a 2017 documentary interview, describing his attacker simply as “pure evil.”
Want to hear this story told in full, first-person detail — including material drawn directly from Gilles Tetreault’s own memoir and newspaper archives spanning the entire investigation and trial? Listen to our two-part episode, “The Kill Room,” available now on Apple Podcasts, Spotify, Amazon Music, YouTube, or wherever you get your podcasts.
Have thoughts on this story or other cases you’d like to see highlighted? Share them with us in the comments or connect with us on social media. Together, we can ensure that stories like this one are never forgotten.
Don’t forget to follow us on social media, share your thoughts, and let us know what you’d like to hear about in future episodes. If you have any true crime stories of your own, send them our way crimeclueless@gmail.com to be featured on a future episode! And as always, remember: refuse to be clueless, careless, or caught off guard. Not today, murderers.
See you in the next episode of Crime Clueless!
If you liked “The Kill Room,” you might also love:
Dave Kroupa, Liz Golyar, Cari Farver — Before there was “Sheena” and “Jen,” there was a different kind of fabricated online persona used as a weapon. This case shows just how far someone will go, hiding behind a fake digital identity, to manipulate and terrorize the people closest to them — a chilling companion piece to Twitchell’s dating-site deceptions. Read more about this case here, or listen to both part one and two on Apple Podcasts, Spotify, Youtube, or anywhere you get your podcasts.
Missy Bevers — Another case built around a literal disguise concealing violent intent. If the image of a masked attacker waiting in the dark stuck with you after “The Kill Room,” this case will too. Read more about this case here, or listen on Spotify, Apple Podcasts, Youtube, or on any podcast platform.
Robert Fisher — Twitchell wasn’t the only man in our archive who built an entire secret life to hide what he was capable of. Fisher’s case is a study in how far someone will go to construct a false narrative around themselves — right up until it collapses. Read more about this case here, or listen to our episode on Youtube, Apple Podcasts, Spotify or anywhere you get your podcasts.
Betty Gore — Like Twitchell, this case hinges on a killer’s own self-defense narrative — and a jury forced to decide how much of that account to believe, weighed against the physical evidence left behind. Read more about this case, starting here, or listen to the first in our three episode series on Youtube, Apple Podcasts, Spotify or on any podcast platform.
Resources:
Books
Lillebuen, S. (2013). The devil’s cinema: The untold story behind Mark Twitchell’s kill room. McClelland & Stewart.
Tetreault, G. (2015). The one who got away: Escape from the kill room. CreateSpace Independent Publishing Platform.
Newspaper Archive (Newspapers.com)
Gelinas, B. (2008, November 2). Filmmaker charged in ‘Dexter’ killing. Calgary Herald, p. 5. https://www.newspapers.com/image/487686003/
Bennett, D. (2008, November 6). Cruelty led to divorce. Red Deer Advocate, p. 3. https://www.newspapers.com/image/559520885/
Stolte, E. (2008, November 10). Horror films best way to examine evil: prof. Edmonton Journal, p. 3. https://www.newspapers.com/image/475917670/
Hanon, A. (2009, January 10). Loose lips cost cases — veteran cop takes public pressure over homicides. Fort McMurray Today, p. 3. https://www.newspapers.com/image/739687928/
Kleiss, K. (2009, July 25). Judge denies bail for filmmaker. Edmonton Journal, p. 23. https://www.newspapers.com/image/475865127/
Zabjek, A., & Gelinas, B. (2009, September 5). Filmmaker to go directly to trial. Edmonton Journal, p. 23. https://www.newspapers.com/image/475854311/
Franklin, J. (2010, September 7). Jury selection underway in bizarre case. The Tribune (Welland, ON), p. 35. https://www.newspapers.com/image/1227445996/
Zabjek, A. (2011, March 14). Murder allegedly mimicked movie. Edmonton Journal, p. 1. https://www.newspapers.com/image/476177000/
Blais, T. (2011, March 15). Jury selection begins in bizarre murder trial. The Sun Times (Owen Sound, ON), p. 8. https://www.newspapers.com/image/726435322/
Gelinas, B. (2011, March 16). Edmonton filmmaker’s murder trial opens. Calgary Herald, p. 9. https://www.newspapers.com/image/488190626/
Zabjek, A. (2011, March 17). Laptop file details murder plan. Edmonton Journal, p. 1. https://www.newspapers.com/image/476181100/
Zabjek, A. (2011, March 17). ‘Diary’ details attack on second man: Crown. Edmonton Journal, p. 4. https://www.newspapers.com/image/476181178/
Zabjek, A. (2011, March 18). Test revealed blood in filmmaker’s garage. Calgary Herald, p. 8. https://www.newspapers.com/image/488193266/
Zabjek, A. (2011, March 19). Blood-soaked knives, pipe found in garage. Edmonton Journal, p. 21. https://www.newspapers.com/image/476189312/
Zabjek, A. (2011, March 19). Notion of fact and fiction expected to be central to prosecutors’ case in murder trial. Edmonton Journal, p. 25. https://www.newspapers.com/image/476189393/
Ibrahim, M. (2011, March 20). U.S. account of murder trial blacked out. Times Colonist (Victoria, BC), p. 8. https://www.newspapers.com/image/509842471/
Zabjek, A. (2011, March 21). Justice 140 characters at a time. Edmonton Journal, p. 1. https://www.newspapers.com/image/475851806/
Zabjek, A. (2011, March 21). Play-by-play coverage from courtroom gives readers a better idea how justice system works, reporter says. Edmonton Journal, p. 2. https://www.newspapers.com/image/475851808/
Zabjek, A. (2011, March 22). Ex-wife of murder suspect tells court of their marital woes. Calgary Herald, p. 3. https://www.newspapers.com/image/488198565/
Blais, T. (2011, March 23). Friends worried over victim’s ‘date’. Fort McMurray Today, p. 5. https://www.newspapers.com/image/739932676/
Twitchell recalls ‘odd’ happenings. (2011, March 24). Fort McMurray Today, p. 5. https://www.newspapers.com/image/739932698/
Bennett, D. (2011, March 25). Accused asked friend to park car belonging to murder victim. Trail Daily Times, p. A5. https://www.newspapers.com/image/1242261599/
The Canadian Press. (2011, March 26). Filmmaker accused of murder cries in court. The Hamilton Spectator, p. 11. https://www.newspapers.com/image/1015258994/
Zabjek, A. (2011, March 26). ‘Something went wrong and you’re involved’. Edmonton Journal, p. 21. https://www.newspapers.com/image/475852311/
Zabjek, A. (2011, March 26). Accusation turning point of police interrogation. Edmonton Journal, p. 28. https://www.newspapers.com/image/475852318/
Zabjek, A. (2011, March 28). Twitter in the courtroom: How much is too much? Telegraph-Journal (Saint John, NB), p. B1. https://www.newspapers.com/image/1076396349/
Zabjek, A. (2011, March 28). Courtroom coverage expanding. Telegraph-Journal (Saint John, NB), p. B2. https://www.newspapers.com/image/1076396350/
Zabjek, A. (2011, March 29). Seized laptop focus of movie-murder trial. The Province (Vancouver, BC), p. 22. https://www.newspapers.com/image/507638128/
Patrolman testifies at trial. (2011, March 30). The Toronto Sun, p. 114. https://www.newspapers.com/image/1340653596/
Cotter, J. (2011, March 31). He ‘crossed the line,’ accused killer told friend on Facebook. The Globe and Mail, p. 10. https://www.newspapers.com/image/1222157010/
Zabjek, A. (2011, April 1). Twitchell trial hears of bones in sewer. Calgary Herald, p. 5. https://www.newspapers.com/image/487912324/
Zabjek, A. (2011, April 2). Man survived struggle in Twitchell’s garage. Calgary Herald, p. 5. https://www.newspapers.com/image/487915769/
McConnell, R. (2011, April 4). Sensationalism stirs up storm of debate. Edmonton Journal, p. 3. https://www.newspapers.com/image/476167580/
Twitchell trial told of blood stains. (2011, April 5). Calgary Herald, p. 4. https://www.newspapers.com/image/487920851/
Blais, T. (2011, April 6). Mark Twitchell points cops to body. Fort McMurray Today, p. 5. https://www.newspapers.com/image/739932958/
Zabjek, A. (2011, April 7). Twitchell admits he lured his victim to garage and killed him. Calgary Herald, p. 3. https://www.newspapers.com/image/487923096/
Zabjek, A. (2011, April 8). Murder suspect admits to his ‘elaborate lies’. The Province (Vancouver, BC), p. 41. https://www.newspapers.com/image/507639573/
The Canadian Press. (2011, April 12). Twitchell no wannabe serial killer: lawyer. Red Deer Advocate, p. 3. https://www.newspapers.com/image/559517096/
The Canadian Press. (2011, April 13). Aspiring Alberta filmmaker found guilty of murder. Abbotsford News Daily, p. A4. https://www.newspapers.com/image/1229252294/
Correction. (2011, April 14). The Globe and Mail, p. 3. https://www.newspapers.com/image/1222134690/
Gelinas, B. (2011, April 14). Twitchell in prison but may be back in court. Edmonton Journal, p. 23. https://www.newspapers.com/image/475913141/
Zabjek, A., & Gelinas, B. (2011, April 15). Johnny Altinger: The tragic death of a victim and hero. Calgary Herald, p. 17. https://www.newspapers.com/image/487973405/
Zabjek, A., & Gelinas, B. (2011, April 15). Victim: Made sure someone knew where he was. Calgary Herald, p. 18. https://www.newspapers.com/image/487973408/
Gelinas, B., & Zabjek, A. (2011, April 16). ‘You’re done, Mark,’ killer told. Edmonton Journal, p. 1. https://www.newspapers.com/image/475914093/
Gelinas, B., & Zabjek, A. (2011, April 16). Diary told whole story of how Twitchell wanted to be a serial killer, and how he murdered Johnny Altinger. Edmonton Journal, p. 4. https://www.newspapers.com/image/475914103/
Zabjek, A., & Gelinas, B. (2011, April 17). Inside the mind of Alberta’s ‘Dexter killer’. Calgary Herald, p. 13. https://www.newspapers.com/image/488042472/
Zabjek, A., & Gelinas, B. (2011, April 17). Fantasy and real life merged into one for aspiring movie producer who wanted to be a serial killer. Edmonton Journal, p. 4. https://www.newspapers.com/image/475914701/
Tweets, Twitchell and transparency [Editorial]. (2011, April 26). Edmonton Journal, p. 16. https://www.newspapers.com/image/475894925/
Henton, D. (2011, May 26). Killer tries to sell sketches of celebs from cell. The Ottawa Citizen, p. 37. https://www.newspapers.com/image/468271892/
Zabjek, A. (2011, June 18). Killer Mark Twitchell won’t face trial on attempted-murder charge. Edmonton Journal, p. 4. https://www.newspapers.com/image/475917466/
Poplak, R. (2012, June 2). Darkest fantasy. National Post, p. 92. https://www.newspapers.com/image/514576107/
Lillebuen, S. (2012, November 13). Murderer trying to revive film career. The Globe and Mail, p. 7. https://www.newspapers.com/image/1221160156/
The Canadian Press. (2012, December 15). Dexter star ‘horrified’ by Edmonton case. The Leader-Post (Regina, SK), p. 28. https://www.newspapers.com/image/498805394/
Hunter, B. (2017, April 15). ‘That man, he was just pure evil’. Edmonton Journal, p. 12. https://www.newspapers.com/image/477026392/
Web / News Articles
Associated Press. (2008, November 14). Suspected killer may have copied Showtime’s ‘Dexter’. ABC News. Suspected Killer May Have Copied Showtime’s ‘Dexter’ – ABC News
A piece of paper exposed accused killer’s lie, court hears. (2011, March 24). The Globe and Mail. A piece of paper exposed accused killer’s lie, court hears – The Globe and Mail
‘You haven’t told us close to the truth,’ police. (n.d.). St. Albert Today. https://www.stalberttoday.ca/local-news/update-you-havent-told-us-close-to-the-truth-police-1274450
Filmmaker Twitchell found guilty of first-degree murder. (n.d.). Global News. Filmmaker Twitchell found guilty of first-degree murder | Globalnews.ca
Man attacked by notorious Alberta killer Mark Twitchell publishes book. (n.d.). Global News. Man attacked by notorious Alberta killer Mark Twitchell publishes book | Globalnews.ca
‘Dexter’ star says he was horrified by Edmonton’s Twitchell movie murder case. (n.d.). Global News. Convicted killer Mark Twitchell looking for love: ‘I enjoy clever storytelling’ | Globalnews.ca
Bloody evidence found early in Twitchell search. (n.d.). Global News. https://globalnews.ca/news/111344/bloody-evidence-found-early-in-twitchell-search
Roberts, T. (n.d.). The man who escaped ‘The Dexter Killer’. CBS News. Gilles Tetreault: The man who escaped from “The Dexter Killer” Mark Twitchell – CBS News
Jailed murderer Mark Twitchell eager to revive film career. (n.d.). The Globe and Mail. Jailed murderer Mark Twitchell eager to revive film career – The Globe and Mail
Mark Twitchell. (n.d.). In Wikipedia. Retrieved 2026, from Mark Twitchell – Wikipedia
The Devil’s Cinema. (n.d.). In Wikipedia. Retrieved 2026, from The Devil’s Cinema – Wikipedia
Dexter-obsessed filmmaker Mark Twitchell kills John Altinger. (n.d.). Oxygen. Dexter-Obsessed Filmmaker Mark Twitchell Kills John Altinger
The Dexter killer – Mark Twitchell. (2020, May 7). Morbidology. The Dexter Killer – Mark Twitchell • Morbidology
Legal Record
R. v. Twitchell, Court of Queen’s Bench of Alberta (2011) (trial proceedings, first-degree murder).
