WAUKESHA, Wis. — A 12-year-old Wisconsin girl who was stabbed 19 times by classmates trying to please a fictional horror character had feared the specter known as Slender Man before the attack, her mother said in an interview aired Friday night.

Payton Leutner was attacked in a wooded park in late May following a sleepover to celebrate her best friend’s 12th birthday. Police say her friend and another 12-year-old classmate later told investigators they spent months planning the attack intended to win favor with Slender Man, the star of numerous spooky stories posted online.

Payton’s mother, Stacie Leutner, said her daughter asked about Slender Man before the attack because stories shared by her friend frightened her. Payton insisted her best friend knew Slender Man was real. Leutner was not overly concerned.

“Fantasy when you are 12 years old is still a very active part of your life,” she said.

Leutner and her husband spoke with ABC’s David Muir for the season premiere of “20/20.” It was their first interview since the May 31 attack in Waukesha County, west of Milwaukee.

Muir went school shopping and to an animal shelter with Payton but did not ask her about the attack and she did not speak on camera.