In the wake of a Wisconsin stabbing that left two 12-year-old girls in custody and another girl fighting for her life, outlets have attempted to explain the fictional creature that allegedly inspired the attack: Who is Slender Man and why were two girls willing to kill for him?

Slender Man, or The Slender Man, first showed up on the website Something Awful in 2009 during a Photoshop contest. The character is often depicted as a slim, faceless man in a suit and tie and sometimes with tentacles. (Via CNN)

The creature came from the mind of Eric Knudsen, who was known on Something Awful as "Victor Surge." Knudsen didn't think his creation would take off.

Knudsen said, "Some people had joked in the thread, 'Wouldn't it be funny if these ended up on paranormal websites?' ... I don't think anyone expected that to happen." (Via TLDR podcast)

But it did, and soon enough Slender Man was showing up all over the web, from sketches to homemade films.

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This video posted to the YouTube account MarbleHornets has more than 1.3 million views.

According to the Milwaukee Journal Sentinel, the two girls that stabbed 12-year-old Morgan E. Geyser 19 times had learned about Slender Man via Creepypasta — a website devoted to scary or unnerving short stories.

The Journal Sentinel reports, "The suspects believed that 'Slender' ... lived in a mansion in the Nicolet National Forest in northern Wisconsin." The suspects said reportedly told police they had to kill to show their dedication to Slender Man and become his "proxies."

But how did this clearly fictional Internet meme become an all-too-real urban legend for the suspects of this vicious crime?

An assistant professor of mass media arts at the University of Georgia told The Washington Post it goes back to how humans interact with storytelling traditions: "Horror stories take on a specific significance and importance because they function metaphorically." The paper adds Slender Man is "an infinitely morphable stand-in for things we can neither understand nor control, universal fears that can drive people to great lengths — even, it would appear, very scary, cold-blooded lengths."

That's one of maybe countless explanations that'll be presented as to why Knudsen's Internet creation reportedly led these girls to attempt murder. Meanwhile, an administrator on Creepypasta posted a message to the homepage.

It reads, "This incident shows what happens when the line of fiction and reality ceases to exist. ... Hopefully, the gruesome crime that happened in Wisconsin will not repeat itself again, and our hearts go out to the families affected by this crime."