The Dexter Wannabe:Mark Twitchell·Johnny Altinger

Mark Twitchell was an aspiring filmmaker in Edmonton, Alberta, with a deep interest in the TV series Dexter. In 2008 he rented a detached garage and posed as a woman on online dating sites to draw men there.

Gilles Tetreault answered one of those profiles in early October and was attacked by a man in a hockey mask with a stun baton. He fought his way out and escaped. On October 10, 2008, Johnny Altinger, who worked in the oil industry, went to the same garage and was killed. Soon after, his friends received emails from his account claiming he had met a woman named Jen and gone to Costa Rica. The story didn’t convince them. When police questioned Twitchell, he volunteered that he had paid a stranger $40 for a red Mazda, and the car turned out to be Altinger’s.

Twitchell was arrested on October 31, 2008. On his laptop, police recovered a deleted document called “SKConfessions” that described becoming a serial killer and matched both attacks. He called it fiction. In April 2011, a jury convicted him of first-degree murder, and he received life with no chance of parole for 25 years. He later dropped his appeal, and in March 2026 the Parole Board of Canada denied his request for escorted leave to visit his parents.