Anissa Weier will avoid prison after a jury in Wisconsin determined Friday she was mentally ill at the time of the stabbing of her fellow classmate, which she said was done in Slenderman's name

One of two Wisconsin girls who stabbed a classmate in 2014 — in the name of a fictional Internet horror character known as Slenderman, they later claimed — will avoid prison after a jury determined Friday she was mentally ill at the time of the attack.

Anissa Weier, 15, was found not criminally responsible for her actions in the 2014 stabbing of classmate Payton Leutner, who was found by a passing cyclist on a bike path of a local park, fighting for her life and begging for help.

Leutner had been lured to the park on May 31, 2014, by Weier and fellow classmate Morgan Geyser. Geyser stabbed Leutner 19 times while Weier urged her on, investigators told the Associated Press. All three girls were 12 at the time.

Both Weier and Geyser told detectives they felt they had to kill Leutner, the AP reported, in an effort to become Slenderman’s servants — which they believed would protect their families from the demon’s wrath. They were both charged with attempted first-degree intentional homicide and initially pleaded not guilty by reason of mental illness or defect.

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Anissa Weier (left) and Morgan Geyser soon after their 2014 arrests
| Credit: Waukesha Police Department

Weier made her first appearance in front of a jury of eight men and eight women on Tuesday in Waukesha County, Wisconsin, where her attorney, Joseph Smith, told jurors in court that her parent’s divorce caused a depressed that descended her into madness as she latched onto Geyser.

“Anissa’s broken mind caused her to lose touch with reality,” Smith said, according to the AP. “Anissa was under the command and control of a delusional disorder.”

That disorder, defense attorney Maura McMahon added in his closing arguments Friday according to the AP, left her believing Slenderman could teleport and read her mind. He would kill her or her family if she talked about him, she claimed.

Prosecutors argued differently, the AP reported, saying Anissa and friend Morgan Geyser “knew this was wrong, they understood what they were doing was wrong.”

Anissa Weier
| Credit: Morry Gash/Pool/AP

On Friday, 10 of 12 jurors — the minimum required by law — voted Weier mentally ill, the AP reported. The same number (though not same jurors) voted she was not criminally responsible for her actions.

Prosecutors had recommend a 10-year prison sentence out of a maximum possible 25 years if Weier was not found mentally ill. Instead, she will go to a state mental hospital and not seek to be released for three years, according to local TV station WISN.

“We are disappointed in the jury’s decision,” the Leutner family said in a statement to PEOPLE. “The decision allows the assailant to petition the court every six months and request release into the community. Their decision also forces our family to relive this horrific crime every six months wondering if they will be released.”

“The potential release of an assailant that methodically planned and executed an attack in which our little girl was stabbed 19 times puts the community and our family at risk,” the statement continued. “It is deeply disappointing.”

Geyser’s trial is scheduled to begin on Oct. 16, the Milwaukee Journal Sentinel reported. Her attorney told WISN they are hoping to negotiate a similar plea with prosecutors as was reached with Anissa.

A spokesman for Payton’s family previously told PEOPLE that she is “a strong young woman who is excelling in school and doing many things that a teenager would do with her family and friends.”