Between 1974 and 1991, Dennis Rader murdered 10 people in Wichita, Kansas. During this time, he sent taunting letters to the police and press, and gave himself the nickname, the "BTK Killer" or "BTK Strangler" - the acronym standing for "bind, torture, kill".
For decades, he evaded detection, and might have even gone his entire life without being captured had he not started sending letters again in 2004. This resurfacing led to Rader's apprehension and subsequent confession in 2005, at which point he was sentenced to 10 consecutive life sentences.
Now, with Rader the age of 73, and more than 40 years after the first murder, we may finally get an explanation about exactly why he felt the need to take so many lives in such an unimaginably cruel manner. Unfortunately, it'll never make up for what he did.
"When I was in grade school, I sort of had some problems," Rader said in previously-unheard audio that has yet to be broadcast in an upcoming two-hour special with Oxygen. "Sexual, sexual fantasies. Probably more than normal. All males probably go through some kind of, uh, sexual fantasy.
"Mine was just probably a bit weirder than other people."
It wasn't until later on in his adult life that Rader actually acted on these "weird" fantasies - by which point he had already gotten married.
Using skills he had learnt in the Air Force and ADT Security Services (an occupation which allowed him to gain the knowledge to disable home alarm systems), Rader began stalking his "projects", breaking into their homes, and murdering them in cold blood.
Speaking about his first victims, Joseph and Julie Otero, the murderer said that he made a spur-of-the-moment decision to strangle them to death.
"I had never strangled anyone before," he once confessed in a court hearing. "So, I really didn’t know how much pressure you had to put on a person or how long it would take."
He added:
"I tried to make Mr. Otero as comfortable as I could. Apparently he had a cracked rib from a car accident. So I had him put a pillow down for his head... I realized that I was already... I didn't have a mask on or anything. They already could ID me. And I made a decision to go ahead and put them down, I guess, or strangle them."
Horrifically, he then went on to kill the couple's two children: 11-year-old Josephine and nine-year-old Joseph.
Eight months later, after Rader had killed a further victim and injured another, the BTK killer contacted a local paper and left them clues about his identity. He also warned them that he would strike again... and he did.
Over the following decade and a half, he would go on to kill a variety of people - some young, some old, some alone, some with their children - but always using similar methods.
"I can live a normal life and quickly switch from one gear to the next. I can become emotionally involved," he disclosed in the newly-released audio. "I can be cold at it. I guess that’s why I survived all those 30 years or 31 years."
During those few decades, Rader had managed to live a double life. He had a wife and two children. He was a Scout troop leader. He went to church. He was, for all intents and purposes, just a "regular" guy.
But his dark fantasies and emotional involvement apparently got the better of him, and he willingly went out and took the lives of 10 innocent people who had no connection to him whatsoever. Explanation or not, Rader is undeniably evil, and stories of his crimes will go on to haunt the Wichita community - and, indeed, the world - for many years to come.