WHAT DRIVES SOMEONE TO KILL? "48 HOURS" GETS A RARE LOOK INSIDE THE MIND OF A MURDERER IN "THE DEXTER KILLER"

Saturday, April 23

Just over a decade after Mark Twitchell was convicted of murdering Johnny Altinger, who prosecutors say was lured into a garage, stabbed and dismembered, 48 HOURS contributor Troy Roberts gets a rare look inside Twitchell's mind through his writings in "The Dexter Killer," to be broadcast Saturday, April 23 (10:00 PM, ET/PT) on the CBS Television Network and streamed on Paramount+.

48 HOURS and Roberts have been covering Twitchell's case since 2008. Now, for the first time on television, investigative journalist and author Steve Lillebuen reveals letters he exchanged with Twitchell during a three-year period. Lillebuen wrote a book about the case titled The Devil's Cinema: The Untold Story Behind Mark Twitchell's Kill Room.

"He wrote me probably 30 or 35 different letters - up to about 350 pages of letters," Lillebuen told Roberts.

Twitchell wrote, "The fact is society in general has a deep and profound fascination with the dark side of human nature."

Twitchell was a filmmaker from Canada who dreamed of making it big in the movies. Prosecutors say he created a fake profile on an online dating site. Posing as a woman, he set up a date with Johnny Altinger, then attacked and killed him before dismembering him.

Investigators say Twitchell was obsessed with the gruesome serial killer at the center of the TV series "Dexter," which airs on SHOWTIME, a division of Paramount Global, which owns CBS.

"Mark Twitchell wrote to me quite extensively about his interest in 'Dexter,'" says Lillebuen.

He says Twitchell "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 pressed Twitchell to explain himself, and Twitchell wrote, "It is what it is, and I am what I am."

"With many serial killers, it's the killing part that they enjoy," says retired FBI profiler Julia Crowley. "And once they've killed a person, they're done. Not Mark Twitchell."

Twitchell also lured another man, Gilles Tetreault, with a similar ruse only one week before he killed Altinger. But Tetreault managed to escape.

Twitchell is eligible to apply for parole next year. Tetreault, who escaped from him nearly 14 years ago, is worried that the convicted killer could come after him.

"I'm scared that he might want to finish what he started and come after me," Tetreault tells Roberts. "I think he's pure evil. ... I would like to see him in jail for the rest of his life."

What drove Twitchell to kill? And should he be released on parole? Roberts and 48 HOURS have the latest on the case.

48 HOURS: "The Dexter Killer" is produced by Asena Basak. Michael McHugh is the producer-editor. Lourdes Aguiar and Anthony Venditti are also producers. Joan Adelman and Michelle Harris are the editors. Patti Aronofsky is the senior producer. Nancy Kramer is the executive story editor. Susan Zirinsky and Judy Tygard are the executive producers.

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