In 2014, two 12-year-old girls lured their friend into the woods while at a slumber party and stabbed her 19 times. The victim was left to die, but was able to crawl to a road, where a cyclist found her and called 9-1-1. On its own, it was a horrific crime, but the assailants’ reasoning is even more frightening. The two girls said they attempted murder to impress an internet phantom called the Slenderman, or else he would kill their families. The crime was so sensational, HBO produced a full-length documentary, Beware the Slenderman, that takes a closer look at the attempted murder and the young girls’ motives. The trailer, which came out today, is utterly chilling.

The Slenderman is perhaps one of the best-known creepypastas, eerie tales and images that have circulated around the internet. He’s described as an extremely tall being, anywhere between 6 to 15 feet tall, with white skin and no distinguishable facial features. He typically wears a black business suit and is known to stalk children. He’s pretty much the boogeyman for today’s internet-dominated culture.

HBO’s documentary examines the two girls’ crime and explores the Slenderman lore. As one of the voiceovers says, “They don’t know how to differentiate between fantasy and reality.”

The Slenderman stabbing trial brought to light a variety of issues, like how dark corners of the internet may negatively impact children. “I am deeply saddened by the tragedy in Wisconsin, and my heart goes out to the families of those affected by this terrible act,” Slenderman creator Eric Knudsen said in a statement in 2014. As the lines between the real world and online world continue to blur, sometimes there are real-world implications for what’s spread on the internet.

Beware the Slenderman premieres on January 23 on HBO.

Photos via YouTube

Gabe is an Associate Culture Editor with a deep love for the internet and memes. He's written for the Daily Dot, Mashable, Mic, and the Daily Beast. Originally from California and now living in Brooklyn, he's always craving Taco Bell.