In 2014, 12-year-old Wisconsin residents Morgan Geyser and Anissa Weier were accused of stabbing their friend, Payton Leutner, 19 times to become "proxies" of the internet myth Slender Man.
Slender Man, an internet boogeyman of sorts, was created by Eric Knudsen on the forum Something Awful in 2009.
The new HBO documentary based on the event, Beware the Slenderman, weaves together home videos, interviews with family members, and footage of the girls' taped confessions.
After the stabbing, Weier and Geyser left Leutner for dead and searched the woods for Slender Man's mansion. Police found them four hours later, six miles from the crime scene.
"The narrative does not revolve around guilt or innocence," Beware the Slenderman 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."
"Above all, it is the anguish and astonishing honesty of the girls’ parents that anchors the film’s narrative to its tragic core."
Weier and Geyser are currently seeking separate trials, and are being held in at a juvenile detention facility. They will return to court Nov. 11.
Beware the Slenderman premieres on HBO on Jan. 23, 2017. There will be a special preview screening at DOC NYC on Saturday, Nov. 12.