Meet Mark Twittchell the “Dexter Killer”

Chilling letters reveal more about the twisted mind of real-life “Dexter” killer Mark Twittchell.

Dexter is a hugely popular TV series that depicts the life of a forensic scientist by day who turns vigilante serial killer by night, hunting down murderers who have not been adequately punished by the justice system due to corruption or legal technicalities.

Mark Twitchell had a self-described “obsession” with the show about a revenge serial, so much so that he had created a “killer room” to dismember bodies just like the show’s main character.

In October 2008, Twitchell pretended to be a woman in a chat room and managed to set up a date with 38-year-old Johnny Altinger, whom he later murdered in cold blood. Twitchell beat and stabbed his victim, then proceeded to methodically dismember him on his garage table.

All indications were that he did it believing himself to be “Dexter,” although the killer denied it, saying there was no connection to the TV show.

Twitchell went back to pretending to be a woman named Sheena and got another date, this time with Gilles Tetreault. The killer attacked him, but Tetreault fought back and managed to escape; the person who had assaulted him was wearing a field hockey mask.

He did not file a police report about the attack until he saw the same mask at the press conference where Altinger’s death was announced; he then notified authorities about the attempt on his life.

“She — she was very attractive looking,” Tetreault told “48 Hours” contributor Troy Roberts of the woman named “Sheena” for the recent broadcast about “The Dexter Killer.”

She sent directions that took Tetreault to a garage, but as soon as Gilles walked in, he was attacked by a man.

“He’s about 6 foot and has a black and gold hockey mask all painted up on his face,” Tetreault explained. “There’s this chill down my back as I — wow, this is no date.”

The masked man ordered him to the ground at gunpoint.

“And he tore a piece of tape, and he covered my eyes with it,” Tetreault recalled. “And I start hearing different things … my head is just racing like it’s like thinking, ‘What’s goin’ on? What’s he gonna do? Is he takin’ another weapon out?'”

After a violent struggle, Tetreault broke free and escaped. Embarrassed and believing he had been a victim of a botched robbery, he didn’t call the police – but when he recognized the mask on TV, he felt obliged to.

Investigative journalist Steve Lillebuen and former FBI criminal profiler Julia Cowley provided information that linked the killer to the Dexter TV series.

“He had a kill room set up with plastic sheeting. He had a table set up for his victims. He had this kind of processing kit that was very similar to what Dexter uses”, Lillebuen said.

Twitchell had sent the journalist some chilling letters that revealed his dangerously disturbed state of mind.

“It would appear that I’m unique in the world. There is no key. No root cause … If I really were capable of premeditated murder … Normal, healthy, well-adjusted 30-year-old men … I once heard the legend of another worthy victim … I dealt with his remains in a disrespectful manner that traumatized me forever … psychopathic serial killer … I quickly grew to resent and hate this man”.

“It’s what it is and I’m what I am.”

“Nobody would side with Dexter Morgan if he went around slaughtering schoolteachers and mail carriers on a whim.”

After Lillebuen released the letters, Twitchell was dubbed “The Dexter Killer” because of the numerous links between the television series and his real-life crimes.

Twitchell is now behind bars for murdering Johnny Altinger, but authorities believe he intended to kill others.