Two 12-year-old girls plotted to kill their friend for months and then stabbed her 19 times to prove the internet monster "Slender Man" was real, police in Waukesha, Wisconsin, say.

The girls have been charged as adults with attempted first-degree homicide and are being held on $500,000 bail, after police say they confessed to stabbing their friend in the woods. Each could face up to 65 years in prison if convicted. Anthony Cotton, a lawyer for one of them, told the Associated Press he would seek to move her case to juvenile court.

Waukesha police said the victim, also a 12-year-old girl, is in stable condition. She suffered suffered stab wounds to her legs, liver, pancreas and stomach, and, in a complaint, police said medical personnel described her as "one millimeter away from certain death".

Police say the two girls waived their Miranda rights and gave statements after they were arrested. Asked by the Guardian why the 12-year-olds had been interrogated without a lawyer present, Captain Ron Oremus of the Waukesha police department said: "If they didn't request we're not providing it … That might happen at a different point when they're charged, that did not happen on our end."

Oremus said the girls' parents were called, and that when they arrived at the station they were informed that their children had waived their Miranda rights, but he did not know when in the interrogation process the parents were told.

The victim was found by a bicyclist who called police just before 10am on Saturday, after the victim told him: "Please help me. I've been stabbed."



Oremus said the suspects were picked up walking on the north side of town, a few miles from where the victim was found.

The criminal complaint says one of the girls told a detective about the horror-fiction website Creepypasta.wikia.com, where she'd read about "Slender Man", a horror-story character invented in June 2009 by Eric Knudson, a user on the comedy and fiction website Something Awful. He included the character in a thread discussing paranormal hoaxes, posting a black-and-white picture showing children playing, to which a sinister shadowy figure had been added using Photoshop.

Since his inception, Slender Man has been the subject of numerous works of fan fiction, from short stories to the ongoing YouTube series Marble Hornets, which has almost 380,000 subscribers and more than 73m views. There are also a series of Slender Man video games; the latest, Slender Rising 2, was released in January.

Since he exists in the collective mind of the internet, descriptions of Slender Man differ. Most stories depict him as tall, wearing a suit, sometimes with tentacles or tendrils coming from his back, and a blank or covered face. Stories variously attribute to him powers of mind control, teleportation, the ability to stretch his limbs at will and to wipe peoples' memories.

In order to prove Slender Man was real, one of the girls told police, according to the complaint, they needed to kill someone.

According to the complaint, the two girls told police they'd been discussing killing the victim since December 2013, whispering about it on the bus and using code words to discuss their plan to kill her and run away to Slender Man's mansion.

According to police, one of the girls originally said they planned to kill the victim late at night inside one of their homes, first duct-taping the victim's mouth shut so she couldn't scream, and then stabbing her in the neck before pulling the covers over her so she would appear to be sleeping. They then planned to escape to Slender Man's mansion.

Instead, after a trip to a local roller skating rink on the night the suspects allegedly planned to kill their friend, the girls changed their minds, according to the complaint, and decided to kill her in the bathroom of a nearby park. When the three got to the bathroom, however, one of the suspects balked.

A short time later, they took the victim to play hide and seek in the woods. There, one of the girls told police that she became squeamish, and gave the other the knife. "I'm not going to until you tell me to," the girl with the knife said, according to the complaint. The other told police she began walking away and said, "Go ballistic, go crazy." Then, she told police, the girl with the knife then said, "Don't worry, I'm just a little kitty cat," tackled the victim and began stabbing her. The other girl told police that she recalled both of them stabbing the victim. "It was weird that I didn't feel remorse," she told a detective, according to the complaint.

"The bad part of me wanted her to die, the good part of me wanted her to live," one of the girls told police.

In a statement provided to the Guardian by an attorney representing one of the girls, the girl's parents said: "We wish to express our deepest sympathies and extend our heartfelt prayers to the victim and her family. Since learning of this tragic event on Saturday, we have been overwhelmed with anguish, both for the victim and our daughter. Our hearts are heavy with sadness as we try to understand what happened. We thank everyone who has reached out to us as we struggle to understand these events. Not a moment passes when we do not think about, and pray for, the victim and her family. We ask that our privacy be respected as this process unfolds and as we try to find answers to these difficult questions."