A psychologist explains the "perfect storm" of circumstances surrounding the Slenderman stabbing of a 12-year-old girl

The case of the Slenderman stabbing — in which authorities say two 12-year-old girls attempted to kill their friend to please a popular Internet horror character — “really was this strange, perfect storm that could only have happened in the way that it did,” psychologist Dr. Abigail Baird tells PEOPLE.

On May 31, 2014, according to police, Morgan Geyser and Anissa Weier lured Payton Leutner, also 12, to the park where she was found alone and stabbed 19 times. Payton survived after a passerby called 911.

“Any parent who reads this story can [see] that their own teen is only one or two clicks away from something similar,” Baird tells PEOPLE in an interview. The attack and its aftermath will be featured in a new HBO documentary, Beware the Slenderman, premiering on Jan. 23 at 10 p.m. ET.

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Anissa and Morgan lived in the same condominium complex and met on the school bus when they entered sixth grade. They liked rollerskating and exploring the Internet. It was there that they learned about Slenderman, a faceless fictional character whose mythology was fueled through videos and mostly teen-created fiction — and their obsession grew.

Morgan, according to her parents, has been diagnosed with early-onset schizophrenia. Anissa has no history of mental illness.

“Anissa had some issues making friends, and all she wanted was friends,” Baird says. “And she happened to make friends with someone who maybe wasn’t the most grounded in reality.”

Anissa Weir (left) and Morgan Geyer soon after the Slenderman stabbing
| Credit: Courtesy Waukesha Police Department

Anissa’s parents say they think about Payton and her family every day while they attempt to make sense of the situation.

“We do not know ‘why’ yet,” Anissa’s father, Bill Weier, tells PEOPLE.

Anissa’s mother, Kristi Weier, says they might never know. “The only person that knows why they did this is 12-year-old Anissa and 12-year-old Morgan,” she says. “Those children, basically, don’t exist anymore.”

Anissa and Morgan, now 15 and 14, are charged as adults, with attempted first-degree intentional homicide, in Peyton’s stabbing.

They have pleaded not guilty by reason of mental illness or defect. If found guilty, they each face up to 65 years in prison.