Moms of guilty teens in 'Slender Man' case speak out

Angie Geyser and Kristi Weier told ABC News they saw no warning signs of violence before their daughters stabbed a classmate.
2:22 | 02/02/18

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Transcript for Moms of guilty teens in 'Slender Man' case speak out
We'll begin with these developments in the slender man case. One of the two girls who stabbed a friend is sentenced to the crime and ABC's linsey Davis is here with the latest. Reporter: Good morning. A tearful apology in court Thursday from Morgan geyser and I'm sorry to her former friend for stabbing her 19 times. The Wisconsin judge still gave her the maximum sentence, a teenage girl who likely won't experience freedom until her 50s because of a crime she committed when she was 12. I just want to let Bella and her family know that I'm sorry. Reporter: Sentenced to a maximum 40 years in a psychiatric hospital, Morgan geyser expressed remorsepin court for the stabbing attack of her friend and 12-year-old classmate Payton leutner. She appears to be stabbed. What? Stabbed. Reporter: The 2014 case known as the slender man stabbing captivated the country. GU geyser and her friend stabbed her 19 times claiming it was to please that fictional character. Leutner miraculously survive and both girls sentenced to decades of institutional supervision for the violent attack. In an exclusive interview ABC's David Muir sat down with the mothers of those teenage girls. The interrogation it general is difficult to watch. Is she dead? I don't know. She was taken to the hospital. That's not my daughter saying those things. That's not the way that she speaks of that's not the way that she agos. It was like looking at a different child. Yes. Reporter: The parents tell David there were no warning signs ofviolence. I did search ?? her II pad. I did watch over her shoulder. Do you feel responsible? I think on some level I'll always feel responsible for not knowing that my daughter wasn't well. As a mother you're supposed to be there to protect your child. Reporter: The judge explained the sentence by saying that geyser who is 15 remains a risk to herself and others and says what we cannot forget this was an attempted murder and David has compelling conversations about that day and the girls now. All coming up on "20/20" at 10:00 eastern.

This transcript has been automatically generated and may not be 100% accurate.

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