Mark Twitchell was a 29-year-old guy from Edmonton, Canada, who wanted to make movies for a living. He went to film school and even made a Star Wars fan movie that had a small part featuring a real actor from the original films. But while Twitchell seemed like a normal person trying to break into Hollywood, he had become seriously obsessed with the TV show Dexter. The show is about a guy who works as a blood expert for the police but secretly goes around killing bad guys. According to Wikipedia, in October 2008, Twitchell rented out a garage in the south part of Edmonton. He told people he needed it to film a short horror movie called House of Cards. His real plans were far grimmer, though. He really thought he could get away with this On October 3, 2008, a man named Gilles Tetreault showed up at the garage thinking he was going to meet a woman he had been talking to online. Her name was supposed to be Sheena, and they had connected through a dating website called Plenty of Fish. But when Tetreault walked into the garage, someone wearing a hockey mask jumped out and attacked him with an electric shock weapon. Tetreault fought back hard and managed to get away. He felt too embarrassed to tell the police what happened. Just one week later, a 38-year-old man named Johnny Altinger fell for the same trick. But Altinger was not as lucky. Twitchell hit him over the head with a metal pipe and then stabbed him to death. Mark Twitchell was a filmmaker who, inspired by the series ‘Dexter’, attempted to become a serial killer by catfishing men online, kidnapping them, and killing them. He successfully lured two men but killed only one. He was caught after that murder and was sentenced to life in… pic.twitter.com/tB1OKAAXCv— Creepy.org (@creepydotorg) October 6, 2025 After Twitchell killed Altinger, he tried to burn the body in a big metal barrel. When that did not work, he cut up the body into pieces and threw everything into a sewer drain. Then he broke into Altinger’s apartment and used his computer to send fake emails to his friends. The emails said that Altinger had met a woman and they had gone on a surprise trip to Costa Rica together. Twitchell even sent an email to Altinger’s job saying he was quitting. But Altinger’s friends knew something was wrong. They got worried when they broke into his place and found his passport sitting there, along with dirty dishes in the sink. It looked like he had not packed anything for a trip at all. They called the police right away. The investigators went back to check the directions that Altinger had sent to his friends before going on his date. Those directions took them straight to the garage that Twitchell had been renting. When the police searched the garage, they found blood on the walls. Twitchell tried to tell them it was fake blood from his movie. But when the cops talked to the actors who were in the film, they said there was no fake blood used when they were filming. Special tests showed there was a lot of real human blood all over the place that you could not even see with your eyes. His case reminds people of other shocking stories like a daughter who turned in her elderly father for being a serial killer. The biggest piece of evidence against Twitchell came from his own laptop computer. Even though he had deleted it, the police were able to recover a file called SKConfessions. The SK stood for Serial Killer Confessions. Right at the start of the document, it said: “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 news media started calling him the “Dexter Killer” because of all the connections to the TV show. But later on, when Twitchell was writing letters from prison, he said that Dexter had almost nothing to do with what he did. Stories like this show how dangerous obsessions can become, similar to a serial killer who hunted criminals before gaining fame online.