The other girl said she sees Slender Man in her dreams. She said he watches her and can read her mind and teleport.
‘‘It’s extremely disturbing as a parent and as chief of police,’’ Waukesha Police Chief Russell Jack said at a news conference ahead of the court appearances Monday.
The girls invited their friend to a slumber party on Friday evening, the complaint said. They planned to kill her during the night so they wouldn’t have to look into her eyes, one girl told police, and then run away. They decided to put it off, but the next day, during a hide-and-seek game in a wooded park, they attacked their friend with a knife. One girl told the other to ‘‘go ballistic, go crazy,’’ according to the complaint.
The victim began to scream that she hated them and started stumbling away, one of the girls told police.
The girls left the victim lying in the woods. She crawled to a road where a bicyclist found her lying on the sidewalk. Police arrived and she gave them the name of one of the girls who attacked her.
She was rushed into surgery, police said.
One of the girl’s attorneys, Donna Kuchler, asked Pieper to remove reporters from the courtroom because she planned to attempt to get her client waived into juvenile court. Pieper refused. Kuchler escorted the girl’s family out of the courtroom, telling reporters only that the family was horrified at what happened.
The other girl’s attorney, Joseph Smith Jr., led her family out of court. He declined to comment.
Both girls are due back in court on June 11 for a status conference.