Where is Mark Twitchell now? CBS' 48 Hours explores Dexter Killer's crimes and letters

CBS News' 48 Hours: The Dexter Killer, based on filmmaker turned murderer Mark Twitchell, aired on April 23, 2022. The episode chronicled the tale of one of the strangest copycat killers in history. Following the murder of Johnny Altinger, the show sheds light on the investigations that led to the aspiring serial killer Mark Twitchell, who literally blurred the lines between cinema and reality.

He was nicknamed the Dexter Killer for his methods of emulating the Showtime drama's lead Dexter Morgan (played by Michael C. Hall). In the latest 48 Hours episode, the show delved deep into the aspiring serial killer's psyche with the help of newfound letters and anecdotes from his time of planning the murder(s).

So what happened to Mark Twitchell's dream of becoming an adept serial killer like Dexter Morgan and where is he now? Read on to find out.

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What happened to Mark Twitchell? The Johnny Altinger story

Mark Twitchell, then 29, was an aspiring filmmaker. He put on the guise of filmmaking to plan out a perfect murder, inspired by his reel-life hero Dexter Morgan. Though he made headlines for the murder of Johnny Altinger, a 38-year-old tech enthusiast from Edmonton, Canada, Johnny wasn't the first victim of the Dexter Killer.

Twitchell used a dating site to catfish men and called them to his isolated rented garage, where he planned to murder them. Posing as a woman named "Sheena," he initially lured Gilles Tetreault to his garage, where he tried to subdue the man wearing a hockey mask.

After realizing that his gun was made of plastic, Tetreault managed to escape his captor, but out of shame did not report anything.

His next victim, Johnny Altinger, was not so lucky. Johnny lived in Edmonton and worked in the quality control department at an oilfield equipment manufacturing company. He was active on dating sites and matched with a woman named Jen. He left to meet Jen after letting his friends know that he would be away for the weekend.

However, when he did not return and his close contacts received suspicious mail saying he had gone to Costa Rica with Jen, they informed the authorities. Luckily, one of his friends had the address to where he was going for his apparent date with Jen. Authorities traced the location and found the garage rented under the name of Mark Twitchell.

After questioning Twitchell, the police singled him out as the prime subject after his story did not hold up. Soon, the police retrieved a document from Twitchell's computer titled "SK Confessions," which had all the details of Johnny's murder. It also had information about an escaped prey. Twitchell told the authorities that the document was a screenplay.

Numerous shreds of evidence were dug up against Twitchell, and despite his fancy explanations, Johnny’s blood in Twitchell’s rented garage and other biological evidence led to his arrest.

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Where is Mark Twitchell now?

Twitchell claimed that he killed Johnny in self-defense after the two got into an argument. He later tried to dispose of the body because he panicked.

In April 2011, Mark was found guilty of first-degree murder and was sentenced to life in prison with the possibility of parole after 25 years. He is still in Saskatchewan Federal Penitentiary and frequently watches Dexter. Steve Lillebuen wrote a book about him.

48 Hours: The Dexter Killer is now streaming on CBS and Paramount+.