2 of her friends, also 12, arrested, charged as adults

• Victim was "one millimeter away from certain death," according to court documents


• Suspects are thought to have planned the attack since February


• They appeared in court Monday to face charges of attempted murder


• Police say the girls, both 12, lured their friend into park after a sleepover,

(CNN) -- They had something to prove to someone they found on a ghoulish website. So, two girls allegedly lured a third girl into a wooded area in Milwaukee over the weekend and stabbed her 19 times, police in Wisconsin said.

The suspects allegedly left the victim to crawl to her own rescue. The three girls, all 12 years old, were friends, according to a criminal complaint.

A bicyclist found the wounded girl alive Saturday, lying on a sidewalk in the city of Waukesha, Police Chief Russell Jack said. She was in stable condition at a hospital on Monday.

The girls were trying to impress a certain "Slenderman," the complaint read. One of the girls encountered the name on a website known as Creepypasta Wiki, which posts horror stories.

Slenderman is the site's supposed leader, and to climb up into his realm, a user must kill someone, one of the suspects told police.

The fictional Slenderman character is an internet meme that often appears in horror stories, videos and images.

Allegedly planned

The two were arrested hours after the victim was discovered Saturday, and they were being held on preliminary charges of attempted first-degree intentional homicide.

The complaint identified the girls as Morgan Geyser and Anissa Weier.

Police: Suspects inspired by Internet

They are being charged as adults and appeared in court Monday. Bail was set for each in the amount of $500,000, according to Waukesha County District Attorney Brad Schimel.

The suspects attended the same middle school as the victim and had a sleepover at the home of one of the suspects Friday night, Jack said.

"Both suspects had a fascination with a fictitious character that often posted" to websites dealing with stories about death and horror, the police chief told reporters at a news conference.

According to the criminal complaint, the suspects had been planning the attack since February.

They first thought to kill the victim by placing duct tape over her mouth while she was sleeping and stabbing her in the neck, the complaint read.

Next, the plan was to kill her in a bathroom where there was floor drain that could make cleanup easier, it continued.

But, finally, the girls decided to do it in a park while playing a game of hide-and-seek, the complaint read.

It states: "As they left for the park ... (the victim) was walking in front of them and Geyser lifted up the left side of her white jacket and displayed the knife tucked in her waistband. Weier stated she gave Geyser a look with wide eyes and, when asked what that meant Weier stated, 'I thought, dear god, this was really happening.'"

Millimeter from death

Some of the girl's major organs were struck, but she survived.

One of the stab wounds was near her heart and she was "one millimeter away from certain death," the complaint read.

According to the complaint, the victim told the bicyclist who found her: "Please help me. I've been stabbed." She was in extreme pain and could only answer questions with yes or no.

Authorities searched for the two other girls, and a sheriff's officer found them walking near Interstate 94, Jack said.

He declined to say whether the suspects had blood on their clothes, but added: "There was evidence that was readily apparent when the two were taken into custody."

That evidence included a large kitchen knife inside a purse that Geyser identified as one of her mother's old purses, according to the complaint.

Both girls spoke readily with police, the complaint said.

Attempts to contact an attorney, believed to be representing them, were unsuccessful Monday.

Read: Dad to teenage suspects: 'Rot in hell'

CNN's Ben Brumfield, Janet DiGiacomo and Kara Devlin contributed to this report.