On the evening of Saturday 31 May, a cyclist discovered a young girl bleeding near Rivera Drive in Waukesha, Wisconsin. She told him that her best friend had stabbed her: nineteen times in all, in the liver, pancreas, stomach and legs, with one knife wound missing a major artery near her heart by only a millimetre.

One of the two alleged assailants – both of whom were 12-year-old girls – told police the crimes were inspired by an Internet boogeyman called Slender Man on the website Creepypasta.wiki. The girls decided that killing their friend was their way to prove that Slender Man was real, and had planned the attack since December. They believed Slender Man lived in the Nicolet National Park in Wisconsin, and they planned to go to his mansion and to become his proxies after the murder of their friend.

Leaving their victim bleeding in the woods, the two alleged attackers walked to a local Wal-Mart.

Slender Man has hit the mainstream, now linked forever linked to this shocking attempted murder. Spawned in 2009 in the Internet’s underbelly at the Something Awful forums – the birthplace of Anonymous, Project Chanology and the Chuck Norris fact meme – Slender Man was created by Eric Knudsen as part of a creepypasta (Internet-specific horror stories)-themed Photoshop thread. In these images, old photos of children have been joined by an ominous tall and tentacled figure looming the background. He is wearing a suit but has no face.

The Slender Man origin story originally constructed him as a kidnapper, but as the myth has evolved his threat has become increasingly amorphous.

With iconographic roots spanning to Salvador Dali’s dream sequence in Alfred Hitchcock’s Spellbound (1945), the fanfic and art that has grown up around Slender Man has consolidated around a number of popular YouTube series such as EverymanHYBRID, TribeTwelve and most of all, the remarkable Marble Hornets. Now almost five years old, Marble Hornets is a masterpiece of amateur filmmaking: by a group of kids in Alabama. Its first series cost merely $500 to make, and can best be described as Stan Brakhage meets The Blair Witch Project. With a major Hollywood film adaptation due to hit screens later this year, it seemed, until recently, that nothing could slow the upward trajectory of the Slender Man success story.

The Slender Man is a creature of an Internet age but his function goes back centuries. The ‘boogeyman’ has variations that span time and space: there’s the khokhan from Azerbaijan, the Bau-bau from Romania, the Saudi Arabian Dojairah and Umna al Ghola and the Guyanan Jumbi, to name but a few. While Slender Man mythology is fledgling and its evolution organic and necessarily messy, in the context of this broader boogeyman history he is intriguing: most of these figures act as warnings against bad behaviour in children and teens.

According to the various stories circulating about Slender Man online (mostly originating from the various YouTube series), this modern folkloric figure manifests at the intersection of technology and young people’s secrets. Taken symptomatically, it is a remarkably potent combination in the contemporary digital age, where adults are haunted by fears of their children’s predominantly hidden online lives. This may take the shape of anxieties about children being preyed upon by sexual predators on the Internet, or their involvement in the awkwardly labelled phenomenon of ‘cyber bullying’. Like the popular Paranormal Activity films, Slender Man fictions promote the belief that survival is reliant upon a specific type of hyper-vigilance linked intrinsically to technology. That youth culture has itself created its own boogeyman to warn against the dangers of having secrets online is telling of the robust self-protection strategies young people are capable of creating amongst themselves.

That is, until the Wisconsin attack.

Before then, the Slender Man could be viewed as fulfilling a crucial psycho-social function, like boogeyman variations before him. But what was once a scary story told before bedtime has been irreversibly mediated and now lives on screen, something that places Slender Man in a whole new historical context. The list of grim precedents is chilling. There’s Japan’s ‘Otaku Murderer’ Tsutomu Miyazaki, who killed four children in the late 1980s allegedly under the influence of anime and slasher films. The gleefully carnivalesque Childs Play films were linked to two particularly notorious cases – the murder of 2-year-old Jamie Bulger in 1993 in the United Kingdom, and the Port Arthur Massacre (the second film in the series was said to be a favourite of gunman, Martin Bryant). As the 2012 Aurora shootings remind us, however, such influences are not solely the domain of horror: John Hinkley Jr.’s attempted assassination of Ronald Regan in 1981 stemmed from a delusion that he was Taxi Driver’s Travis Bickle.

In these cases, the pop-cultural-artefact-as-scapegoat strategy is far from opaque: demonising a media product is undeniably more manageable and clear-cut than tackling thornier issues like mental health or gun control. But the Wisconsin Slender Man stabbings – for that is how they will now be remembered – has the added complication of the involvement of children.

The cultural meaning of childhood has fluctuated across cultures historically, but in the West in the last few hundred years, it is normatively aligned with innocence (peppered playfully, at worst, with what we call in a saucy Nigela voice ‘naughtiness’).

When children behave in ways beyond what can be dismissed as mere mischievousness, we evoke an angel/devil binary en masse. In recent days, news reports have appeared implying that the father of one of the alleged Wisconsin attackers was not only aware of his daughter’s interest in Slender Man, but actively encouraged it by placing one of her fan drawings on his Instagram only weeks before the attack. This sad, brutal story has been reduced to one of ‘evil’ children, and now is morphing almost inevitably into a case of of ‘bad’ parenting.

But are words like ‘bad’, ‘evil’, ‘good’ and ‘innocence’ that useful? Beyond the colossal and increasingly urgent need to address mental health and gun control, we need to be conscious of the way that these stories circulate. Reducing children to a good/evil binary harms them, and it harms us. Until we can address these people as people – albeit smaller ones with less experience in the world – we are doomed to keep them alienated and afraid. And it is for young people (the majority of who don’t try to stab their best friends) that Slender Man and other creepypasta are vital. Such figures offer a vast number of kids a shared point of reference, an outlet for their non-Disney sanctioned feelings. They form the basis of robust fan communities, and propel a daily avalanche of creative fan output in the form of art and fiction. For some of the weirder kids – the bullied ones or the ones facing abuse at home – the experience is not killing them, it’s keeping them alive.