MADISON, Wis. (AP) — A Wisconsin woman, Morgan Geyser, linked to one of the most notorious cases involving the online horror character Slender Man, is missing after she removed her electronic monitoring device and left a group home, according to authorities.

On Sunday, Madison police issued an alert for the 23-year-old, stating she was last seen around 8 p.m. Saturday with an adult acquaintance. Police urged the public to call 911 if Geyser is spotted, emphasizing her removal of a monitoring bracelet from the Department of Corrections.

This year, Geyser was placed in a group home after being granted conditional release from the Winnebago Mental Health Institute, where she had been held since 2018. She pleaded guilty to attempted first-degree intentional homicide for her role in the 2014 stabbing of classmate Payton Leutner.

Geyser and her friend, Anissa Weier, were just 12 years old when they lured Leutner to a park after a sleepover, with Geyser stabbing her more than a dozen times while Weier encouraged the attack. Leutner survived the horrific ordeal, albeit with severe injuries.

According to investigations, the two girls claimed they attacked Leutner in a bid to become Slender Man’s servants, driven by a fear that he would harm their families if they didn't comply. Weier, who also faced charges, pleaded guilty to attempted second-degree intentional homicide and was released from a psychiatric facility in 2021.

The Slender Man character, originally conceived by Eric Knudson in 2009 as an internet meme, has since been featured in various media, including video games and a film.

Authorities are urging anyone with information about Geyser's whereabouts to reach out immediately, as her case continues to captivate public interest.