‘Dexter Killer’ Mark Twitchell Catfished Men Before Brutally Murdering & Dismembering Their Corpses In His Garage

The film industry has been under fire quite a bit as of late for the predatory behavior of some men within the industry, but Mark Twitchell was a different kind of predator. Committed to his career in film, he spent his time obsessing over movies like Star Wars and shows like Dexter. Though Dexter has long since touted a wide range of fans throughout the years, few have probably resonated with the character quite as much as Twitchell. In his eyes, Dexter was an inspiration.

mark twitchell behind news camera photo

Finding Victims

For women, the world of online dating has been an almost constant concern. Though it is nice to be able to get to know more people in your area, it certainly comes with quite a bit of risk. Mark Twitchell saw online dating as a hunting ground, not for women, but for men.


Twitchell was obviously driven by the urge to kill and spent his time marveling over crime and gore, but he still had to find victims. It is unclear what Twitchell was looking for in his victims, but he seemed to enjoy cat-fishing them to lure them to him. In multiple different instances, he pretended to be a woman on dating websites to convince his victims to come to him.

mark twitchell dating profile

The Attacks

While pretending to be a young woman, Twitchell would use his creativity for dark intent. He seemed to enjoy convincing the victims that he was someone genuinely interested in them, making it even more heartbreaking when he would attack. In both instances, Twitchell would lure the men to a location and then attack them. His first victim, Gilles Tetreault, managed to escape with his life after being attacked with a stun baton by Twitchell in a mask.

His second victim, John Altinger, wasn’t as lucky. His friends and coworkers listened to John talk about how excited he was for his big date. He seemed to really connect with the woman that he had been talking to and left work in high spirits on the night of his date. When he never returned, his friends and coworkers began to worry. Shortly after, his office received a resignation from John that simply didn’t seem to add up. The letter claimed that he would be leaving the country. Worried, his friends went so far as to break into his condo and ultimately learned that he had not packed a bag and his passport was in the apartment. There were even dirty dishes. Police were able to take on the investigation from that point.

The Confession

When Twitchell was first questioned by the cops, he claimed to have met John Altinger right before his trip to Costa Rica. Police found this highly suspicious and went on to arrest Twitchell. With access to his home, they were able to locate further evidence to tie him to the murder and attempted homicide. Not only were police able to find the mask that he wore, but they found a disturbing document on his computer.

Twitchell had attempted to delete a document titled Serial Killer Confessions, but police were quick to see through this and went through it. The document was a full recount, documenting the murder and dismemberment of Altinger. When questioned, Twitchell claimed that he had killed Altinger in self-defense and written a fictional story about an intentional murder to help him cope.

Police did not for an instant believe that this was the case and were shocked by the detail he went into. His obsession with Dexter was clearly present in the document, making it all too obvious that he was happy to document his jarring tale. In addition to this document, another was found where he referred to himself as a psychopath and carried out a sort of self-analysis talking about how evil he was.


In the end, Twitchell was only charged for the homicide because the attempted murder charge would not have added to his sentence since he will already live and die in prison. Disturbingly, Twitchell has been able to happily catch up on one season after another of Dexter during his time in prison. He shows no interest in changing his twisted ways any time soon.

BreeAnn is the host and creator of Among the Dirt and Trees—and the team blogger! She grew up with a love of all things spooky while obsessing over Investigation Discovery shows and eventually switched over to podcasts while working a boring office job in Corporate America. She has since left her corporate life behind to spend her days and nights as a freelance writer and podcaster, but she still takes time to listen to podcasts while she works. Talkocast has given her a chance to leverage her B.S. in Psychology and her love of writing to terrify the general public. You can find her writing stories, reading books, playing D&D, or doing yoga when she’s not researching cases filled with unimaginable horrors and scaring people out of their next camping trip.

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