"I’m only a little kitty cat." Morgan and Anissa's haunting words as they stabbed their friend.

As Anissa Weier and Morgan Geyser held down their friend Payton Leutner in the Wisconsin woods, they stabbed her 19 times.

On May 31, 2014, the morning after a sleepover party, the three girls visited a local park to play.

While walking to the park, Payton was walking ahead when Morgan and Anissa dropped behind. It was at this moment that Morgan revealed to Anissa what she was hiding under her jacket: a kitchen knife with a black handle.

The trailer for Slender Man Stabbing: The Untold Story. Post continues below video.

Anissa suggested a game of hide-and-seek before the girls set after their friend, held her to the ground and continuously stabbed her.

“Don’t be afraid, I’m only a little kitty cat,” Morgan told their victim before she and Anissa fled, leaving Payton for dead near the playground where the three girls had just been playing hide-and-seek.

One stab wound missed a major artery in Payton’s heart by the width of a human hair. Despite her injuries, and barely able to talk, Payton dragged herself to a nearby path where she was found by a passing cyclist.

Miraculously, she survived.

It was the horrifying 2014 attack by two 12-year-old girls on their classmate that caused a moral panic, after Morgan and Anissa claimed they had attempted to murder Payton for the internet character Slenderman, a supernatural character with a black suit, blank face and long-slender arms that originated as a meme.

In a new documentary, cyclist Greg Steinberg explained what happened when he found the young girl on the side of the road.

“I looked and there was a girl laying there –  a young girl, and she looked so comfortable, I thought maybe she was laying in the sun,” he told Crime+Investigation.

“She looked up at me and said ‘Could you help me please?’ She said that she’d been stabbed multiple times.”

Morgan and Anissa, who were also 12 years old at the time of the attack, told police they attempted to kill Payton to protect their families from Slenderman.

They said they believed that once the murder was carried out, they would prove their loyalty to Slenderman and serve as his servants in his mansion, which they believed was located in the Nicolet National Forest.

A psychiatrist for Morgan, who was diagnosed with paranoid schizophrenia before her trial, said his impression of her was that she was smart but appeared to be psychotic.

"She believed that one of the Teenage Mutant Ninja Turtles was real and that she could talk to him and she believed Slenderman was real and was watching her," he said, reported by The Mirror.

"She thought Slenderman could probably read her mind and she had to be careful even about what she thought.

"She thought her family was in danger because of her involvement with Slenderman. There were a number of things she believed that were disturbing."

In a clip from her interrogation, Morgan confessed: "I might as well just say it, we were trying to kill her.

"Will I regret giving you this information later?"

Anissa, now 16, pleaded guilty to being a party to attempted second-degree murder but was found "not guilty by mental disease or defect". She was sentenced to 25-years-to-life, with a least three years in locked confinement, and treatment in a psychiatric institute until age 53, or her symptoms are resolved.

Morgan, now 17, was sentenced to 40 years under a mental health facility's supervision. Earlier this year she appealed her sentence, claiming she should not have been tried as an adult and did not understand her rights when questioned by police at age 12.

Talking to Crime+Investigation's documentary, prosecutor Kevin Osborne said Peyton, who has never spoken publicly about the crime, will "always be the girl that was almost stabbed to death by two 12 year olds".

"And that will never go away. People that know the story will be reminded of this story.

"People that don’t know the story will ask what happened. Because of the nature of the crime, there is gonna be a stigma that’s gonna go along with these girls for the rest of their lives."