Letters offer a rare look at the thoughts of "The Dexter Killer": "It's what it is and I'm what I am."

This story previously aired on June 10, 2023. MARK TWITCHELL [graduation video]: "I'm glad I got to work with you all and I hope I see you all in the industry." DETECTIVE [interrogation]: Altinger … Does that name ring a bell to you or mean anything to you? MARK TWITCHELL [interrogation]: I'm working on a comedy right now. Which is a — it's actually a full-blown feature that's actually gonna have a decent budget in the neighborhood of about three-and-a-half million … MARK TWITCHELL movie interview]: "The word has gotten around that I'm making a 100 million dollar movie for 60 grand, and some production and directing jobs have already come my way." DETECTIVE [interrogation]:  I mean it's kinda odd that you're filming that kind of thing. DET. BILL CLARK [interrogation]:  So, as you know Mark, we're just here trying to find this John fellow. John Altinger. MARK TWITCHELL [interrogation]: This guy, uh, taps on my window …  you know, "Hey buddy do you wanna buy a car? … I — I've shacked up with this really rich lady …  She's even gonna buy me a new car … so I'm just looking to unload mine… how much do you have on you?" DET. BILL CLARK [interrogation]:  There's absolutely no doubt in my mind that you're involved in the disappearance of John Altinger. No doubt in my mind at all Mark. "SK CONFESSIONS" PASSAGE: "I plunged the knife deep into his neck …" DET. BILL CLARK [Mark Twitchell interrogation]: As I told you that night, I knew that you were involved in the disappearance at that time of Johnny Altinger. That's changed slightly … I now know that you killed John Altinger. DET. MARK ANSTEY [to reporters, holding up hockey mask]: We have some details on this male victim who was attacked, and we would like him to come forward. DET. MARK ANSTEY [to reporters]: To date we do not know who this victim is…. I believe the victim entered the garage and was attacked by another male who was wearing a hockey mask … DET. MARK ANSTEY [to reporters]: We have not found John Altinger's body. GILLES TETREAULT [police interview]: I was off balance, I couldn't run … I fell down on the gravel driveway and, uh, basically crawling. … So, he dragged me back to the garage. "SK CONFESSIONS" PASSAGE: "I grabbed him by the leg as if to drag him back into the garage caveman style." GILLES TETREAULT [police interview]: After this all happened, I realized how lucky I was.  "SK CONFESSIONS" PASSAGE: "Please stop hitting me … oh my skull." DET. BILL CLARK [interviewing Twitchell]: I'm gonna go get the car ready.  We're gonna take a drive. DET. BILL CLARK [to Twitchell in police car]: So, in order to finish the movie, we have to find the body, take it back to the people, the family — done.  Movie's over. And you can write it all down.  DET. BILL CLARK [to Twitchell in police car]:  Look familiar Mark? Are we parked right on top of the sewer where you dumped the body? DET. BILL CLARK [to Twitchell in police car]: So here we are back at the killing garage. The "Dexter" garage.

These are the words of Mark Twitchell, written to investigative journalist and author Steve Lillibuen: MARK TWITCHELL: No. MARK TWITCHELL: Mm hmm. MARK TWITCHELL:  Mm hmm. MARK TWITCHELL: Why? OFFICER [to Twitchell outside garage]: Bring back any memories? You wanna tell us where the body is now?  Get this over with? 

Steve Lillibuen [reading letters]: "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." DETECTIVE: Never heard it before? DETECTIVE:  And we end up going to that garage because of a missing person who supposedly went there.