Rising Sun, Ind., is a sleepy town on the Ohio River with quaint streets, 100-year-old buildings, and benches along the riverfront that beckon you to sit and contemplate. But every once in awhile there's a surprise here, and that came on Nov. 28, 2009.
Late one night, Andrew Conley, 17, walked up to the phone outside the Rising Sun Police Department and reported a crime so horrific and unusual that even seasoned detectives were disturbed by it.
Conley had murdered his own brother, 10-year-old Conner. He had strangled him with his own bare hands.
"He asked me to stop and I just couldn't," Conley told "20/20."
"It hit me that I had just killed my brother and that I was going to be what I thought I was going to be all along -- a monster," Conley confided to police.
Det. Tom Baxter has been in law enforcement for more than 20 years and led the interrogations of Conley.
"In the manner that he talked to me was, almost as though, 'I'm sorry you have to hear this because I'm assuming you've never heard anything so terrible before,'" Baxter said.
Equally terrible to some were Andrew Conley's fascination with the fictional serial killer Dexter Morgan from Showtime's hit series, "Dexter."
"The fact is, he has said on numerous occasions he had fantasized about killing people," prosecutor Aaron Negangard told "20/20." "He told us he was reading books about it—on serial killers. He was watching Dexter."
Indeed, just an hour into his first interrogation with police, Conley told them, "I don't know if you've heard of it, but it's called 'Dexter', and it's on Showtime. And I feel like him because he's a serial killer of bad people…but I just feel like him."
But it remains a mystery as to why Conley killed his little brother. Even when pressed by "20/20" during a three-hour interview, there were few answers.
"I don't know," was Conley's repeated response. "I'm just a person that did a horrible thing and I shouldn't be alive for that."
Like many real psychopaths, the fictional Dexter Morgan's harrowing exterior hides a disturbing hollowness inside. As Dexter himself says in season one, episode one: "People fake a lot of human interaction, but I feel like I fake them all. And I fake them very well."
That sounded much like Conley just 24 hours after disposing of his brother's body in nearby woods.
"I don't see why sometimes people get so happy over something or upset over a little thing," Conley told police. "I just sit there with a blank face."
"I don't know how you could commit a crime like that and not be emotional about it," said Det. Baxter. "No tears. Just an explanation."
Extensive pre-trial interviews conducted with psychologists, psychiatrists, friends and family also shed scant light on an immediate cause, but one of Conley's closest childhood friends did tell "20/20" there was "massive amounts of neglect throughout his childhood" and that Conley's family "just kind of ignored him." Andrew Conley's mother, Bridget Conley, would not talk to ABC News on camera.
Dr. Edward Connor, one of four doctors who evaluated Andrew Conley shortly after the murder, wrote in his psychological assessment that Conley, "struggl(ed) with various severe psychiatric symptoms throughout his latency and young adolescent years."