A few years ago, the internet exploded with stories, video games, and YouTube videos dedicated to the story of Slenderman.

I myself was guilty of telling my friends about a new video game, Slender: The Eight Pages, which required the player to roam around a creepy forest in search of eight pages while Slenderman followed you in the shadows.

After the launch of the original game, countless stories were posted to Creepypasta, a popular website dedicated to horror stories. Granted, stories were published on the website before this as well, but the popularity of the story led to more and more on the site. YouTube channel Marble Hornets also gained more notoriety with their web series as the story gained more publicity. Their first entry, published over nine years ago, has over five million views on YouTube.

For the most part, the viral sensation seemed like mindless, supernatural fun. It was only when a case broke out in Waukesha, Wisconsin in 2014 that the fun came to a screeching halt.

Two girls, both 12 at the time, lured their friend into a forest during a sleepover. They then proceeded to stab her 19 times in the chest, abdomen, legs, and arms before leaving her for dead. Despite her injuries, victim Payton Leutner survived the attack and returned to school three months later.

Upon their arrest, both girls claimed their heinous act was committed because of Slenderman. Both girls claimed they wanted to please Slenderman. They also claimed that if they didn’t go through with the act, they believed that Slenderman would murder their families.

The two girls (Morgan Geiser and Anissa Weier) are now facing time in prison, potentially being tried as adults according to The Guardian. The article, “Slender Man stabbing: Wisconsin girls to be tried as adults, appeals court rules” published on July 27, 2016 states, “The girls have been charged with attempted first-degree intentional homicide and if convicted could go to prison for up to 65 years. As juveniles, they could be incarcerated for up to three years then supervised until age 18.”

“The narrative does not revolve around guilt or innocence,” director Irene Taylor Brodsky said in a statement from HBO, “but instead the court’s deliberation whether the girls should be tried as adults or children.”

This tragic case has now inspired plans from HBO to release a new documentary, Beware the Slenderman. Set to come out in January 2017, the documentary follows the trial of those accused, Morgan E. Geyser and Anissa E. Weier, and the impact internet sensations clearly tend to have on the public, especially children.

The trailer, released on Friday, begins with a rhyme about Slenderman before quickly delving into the phone call between the cyclist who found Leutner and the police. The rest of the trailer focuses on quotes from the girls’ parents, and video tapes of police interrogating Geiser and Weier upon their arrest.

The official explanation for the documentary states: “Shot over 18 months with heartbreaking access to the families of the would-be murderers, the film plunges deep down the rabbit hole of their crime, a Boogeyman and our society’s most impressionable consumers of media. The entrance to the internet can quickly lead us to its dark basement, within just a matter of clicks. How much do we hold children responsible for what they find there?”