The Dexter Killer: How murderer Mark Twitchell copied lethal reel life to brutal real life

'Dateline: The Smoking Gun' delves into Mark Twitchell's gruesome double life as the ‘Dexter Killer’
Mark Twitchell was called the Dexter killer (@cbs)
Mark Twitchell was called the Dexter killer (@cbs)

LOS ANGELES, CALIFORNIA: In the latest episode of 'Dateline: The Smoking Gun', titled 'Deadly House of Cards,' viewers are plunged into the disturbing case of Mark Twitchell, infamously known as the "Dexter Killer." Twitchell, an aspiring Canadian filmmaker, became a murderer after obsessively emulating the fictional serial killer, Dexter Morgan. He lured victims to a rented garage under the guise of filmmaking, but his intentions were far more sinister.

This episode explores Twitchell’s meticulously crafted plot, culminating in the brutal murder of John Brian Altinger. Through exclusive interviews and shocking new revelations, 'Dateline NBC' examines how a man with dreams of Hollywood fame transformed into a real-life villain, leaving a community forever scarred.

Who is film director Mark Twitchell?

Mark Twitchell, born on July 4, 1979, in Edmonton, Alberta, sought to make a name for himself in the film industry. He graduated from the Northern Alberta Institute of Technology's Radio and Television Arts program in 2000 and began working on small projects, including a 'Star Wars' fan film and a short horror movie titled 'House of Cards' in 2008.

However, his aspirations took a dark turn when he was arrested in 2011 and subsequently convicted of first-degree murder for the killing of John Brian Altinger. This shocking crime drew media attention not only for its brutality but also for Twitchell’s chilling inspiration from the TV series Dexter.

Mark Twitchell was a film director (@cbs)
Mark Twitchell was a film director (@cbs)

How did Mark Twitchell meet John Brian Altinger?

Mark Twitchell met John Brian Altinger through a fraudulent internet plot. In 2008, Twitchell had gone onto the dating website Plenty of Fish and created a profile wherein he posed as a female. He furthered this ruse by indicating that she wanted to meet men and he gave an address to a garage he had rented in Edmonton as her location.

On October 10, 2008, Altinger, a 38-year-old oil field worker, believed he was going on a date. After sharing the location with friends, he arrived at the garage, only to be confronted by Twitchell, who then brutally attacked and murdered him.

In a bid to cover his tracks, Twitchell sent e-mails from Altinger's account to the latter's friends and workplace, informing them that Altinger had gone off to Costa Rica on a spur-of-the-moment trip. When Altinger's friends became suspicious and the police investigated, they found evidence leading back to Twitchell, including blood in Twitchell's car and incriminating messages on his laptop. Eventually, this led to Twitchell's arrest and conviction for first-degree murder.

Mark met John on a dating website (@cbs)
Mark met John on a dating website (@cbs)

Why did Mark Twitchell kill John Brian Altinger?

Mark Twitchell killed John Brian Altinger in furtherance of a warped scheme to act out his fantasy to become a serial killer based upon the fictional character Dexter Morgan from the television series Dexter. Twitchell was especially taken with the concept of leading a double life similar to Dexter, who, within this series, was a vigilante serial killer. He even wrote about it, and the experience, prosecutors said, in some sort of "kill room" scenario he had set up in a garage in Edmonton, Canada.

Twitchell lured Altinger into the garage by posing as a woman on the dating website, it was here he intended to kill Altinger and dispose of his body in a matter strongly resembling scenes from Dexter. For Twitchell, this constituted the actualization of violent fantasy in real life, an action he had documented in his script, detailing exactly the steps he took to kill and dispose of his victim.

After the murder, he attempted to fabricate a story of Altinger’s escape to Costa Rica, but his deception unraveled when Altinger's friends became suspicious and contacted the authorities, leading to his arrest.

Mark Twitchell killed John as his obsession (@nbc)
Mark Twitchell killed John as his obsession (@nbc)

How many people did Mark Twitchell kill?

Mark Twitchell was convicted of killing John Brian Altinger in October 2008. Although he killed only Altinger, he also attempted to murder another man, Gilles Tetreault, using a similar method.

Fortunately, Tetreault escaped with his life, highlighting Twitchell’s dangerous potential as a serial killer. His obsession with violent fantasies culminated in the tragic death of Altinger, but his ambitions were cut short by his arrest and conviction.

Mark Twitchell killed John in 2008 (@cbs)
Mark Twitchell killed John in 2008 (@cbs)

Where is Mark Twitchell now?

Mark Twitchell was sentenced to life in a Canadian prison for the first-degree murder of John Brian Altinger. In 2011, he was convicted and received a life sentence with no possibility of parole for 25 years. It simply means that Twitchell will be behind bars until at least 2036 when he could be eligible for parole. Twitchell is serving his sentence at Saskatchewan Federal Penitentiary in Canada.

John Altinger was a computer enthusiast (@cbs)
John Altinger was killed by Mark (@cbs)

Uncover Mark Twitchell's sinister case in 'Dateline: The Smoking Gun' on Thursday, October 24 at 8 pm on Oxygen.

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