From a NY Times review of a new book about the 2014 Slenderman attack; it turns out, as with most hard-to-understand human behavior, that mental illness was at the root:
Three sixth graders — Payton “Bella” Leutner, Morgan Geyser and Anissa Weier — went into a wooded park to play hide and seek. While Anissa watched and offered encouragement, Morgan stabbed Bella 19 times with a kitchen knife. Bella, left for dead, managed to stumble and crawl to a nearby road for help; Morgan and Anissa were soon taken into custody by the police.But a key part of the story is what happened after the kids were arrested:
What had happened? What drove two 12-year-olds to try to kill one of their friends? Morgan, it turns out, had become obsessed with a website called Creepypasta.com, a wiki of scary stories and urban myths; the ones which gripped her were about a murky figure called Slenderman. Hale writes, “When [Morgan] came across Slenderman, she was captivated. She had seen his face before. Not on the internet, but in her home. He was the spitting image of It, the tall, faceless man who had plagued her since she was young.” As the site and the stories were crowdsourced, information about Slenderman spread all over the internet — kids made new photos, posted new stories. There was even a video game.
As the story unfolds, it becomes clear that Morgan, whose father has schizophrenia, is showing signs of the illness herself. To her, Slenderman is both a threat and a hero, someone who understands her terrifying visions and fears: “Every hallucination that had ever scared her, thrilled her or comforted her became projected onto Slenderman.”
It’s unclear whether it was Morgan or Anissa who first came up with the idea of becoming proxies for Slenderman, because “if they didn’t do his bidding” — that is, murder for him — “he would kill everyone they loved.” Bella, an eager-to-please girl, was the ideal target. Morgan said she knew Bella would follow them into the woods, even if it was spooky: “People that trust you are very gullible.” Anissa insisted, “We thought we had to for real kill someone.”
In jail, “the trauma of the stabbing sent Morgan’s symptoms into overdrive,” Hale writes, describing the child’s unfocused eyes and her conversations with people no one could see. Morgan believed that Slenderman would come to rescue her and help her puzzle out the strange, violent thoughts that filled her head.
As for explanations, well, crazy people sometimes do crazy things.
The other part of the story needing explanation is the behavior of the state of Wisconsin, which charged two clearly messed-up 12-year-olds as adults, jailed them for years, and refused to treat Morgan's budding schizoprenia.
This case fits into our society's fears in the same horrible way that Slenderman fit into Morgan Geyser's fantasies. We are afraid that the disturbing stories and images we consume for fun will have terrible real-world consequences, that somehow we will be punished for our dark obsessions. We fear the violence and disorder that we sense all around us, lurking behind closed doors, behind the faces of people on the street. We hear it in Black Metal music, or gangstah rap, or in the theme from The X-Files. We worry that the internet is spreading some kind of insidious poison. So when the darkness we fear did break out we reacted with punitive violence, directed as much against ourselves as against two 12-year-olds.