Don't watch these at night. You've been warned!

Serial killers have fascinated society for decades. What causes someone to cross that line? Is it something that happened to them during childhood? Are some people born with a desire to kill? Is it a problem that science may be able to solve in the future?

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The following are serial killer documentaries now streaming on Netflix that will keep you up at night. These docs are as illuminating as they are deeply creepy.

The Confession Killer is a Netflix documentary series based on Henry Lee Lucas, known as one of the world's most notorious serial killers. He boasted of killing hundreds of people, and was convicted of murdering 11.

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That isn't why this documentary will keep you up at night. The investigation itself is skin-crawling. You'll have to check out the documentary to find out why.

An infamous face of evil, Richard Ramirez is otherwise known as the Night Stalker. Ramirez had a horrible childhood full of abuse. His alcoholic father beat him. His older cousin Miguel (who was also a serial killer) would show Richard pictures of the women he raped and dismembered while fighting in the Vietnam War. Richard would sometimes sleep in a nearby cemetery to escape his father's beatings.

Ramirez's troubled childhood laid the foundation for the monster Richard would become. Richard molested, raped, degraded, and tortured his victims. The Night Stalker: The Hunt For A Serial Killer not only goes into the deeply troubled mind of Ramirez, but the strain on the police force to catch him before he tortures and kills another victim.

David Richard Berkowitz is known as the Son of Sam, and the 44- Caliber Killer. He is a serial killer who said a demonic dog owned by a man named Sam ordered him to kill people with a 44-caliber pistol. The Sons of Sam documentary questions if Sam acted alone, and it's an unsettling descent into obsession and madness. The documentary shows just how fragile the human mind can be when faced with evil.

An interesting side note that the documentary doesn't detail: Darrell Scott, the father of Rachel Joy Scott, a teenage girl who was murdered during the Columbine Shooting, is now friends with David Berkowitz because of his kindness and compassion. Berkowitz, who now claims to be a follower of Christianity, said Rachel's story and vision moved him to start a chain reaction of kindness to combat the evil in the world.

The Netflix original documentary series Don't F**k With Cats is chilling because it is like watching the making of a serial killer. The series follows a group of amateur investigators trying to figure out the identity of a man who enjoys torturing and videoing cats.

Killing and torturing animals is a common trait among serial killers, and watching someone mature and grow in their desire to kill is undeniably scary. The documentary is disturbing because no rational person wants to see animals hurt, especially cats. But Don't F**k With Cats shows how would-be serial killers' desire to kill starts with small animals and then moves on to human victims. They are just regular everyday people with something dark going on within, and can even be your coworkers or neighbors.

The documentary series The Raincoat Killer is chilling in recounting the brutal way the killer murdered his victims without remorse. The Raincoat Killer documentary series investigates a South Korean killer who would murder his victims with a hammer. Yoo Young Chul mostly murdered sex workers and wealthy elderly women.

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Yoo Young Chul confessed to eating the flesh of his victims. He dismembered his victims to keep law enforcement from identifying them. The series is not for late-night viewings unless you desire nightmares.

Ted Bundy was handsome, charismatic, charming, intelligent, volunteered for the suicide hotline—and was a serial killer. What makes him so frightening is that he could have led a good life as an attorney, but chose to brutally murder women instead. The Conversation tapes are chilling in the nonchalant way Ted Bundy talks about his crimes. He might as well be talking about eating a Big Mac, not his life as a serial killer.

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Ted Bundy admits to not feeling guilty about anything he has done. He acknowledged that he didn't close part of his mind or dissociate. He understood everything he did, and didn't feel any guilt or remorse for his crimes. That makes the series scary; it would be hard to sleep at night after watching it.

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Kevin Frasure is a horror author and film geek. He has been featured in Fear and Trembling Magazine, Magic Methods in Screenwriting, and Morbidly Beautiful. He is an avid horror fan and enjoys a good horror novel or a binge-watching horror movie night while eating pizza. He is also a copywriter for non-profit organizations. He is a writer for Collider.

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