Disturbing new details emerged Monday from the preliminary hearing for Morgan Geyser and Anissa Weier, the Waukesha, Wisc., teens accused of stabbing their friend 19 times to appease the fictional Slender Man character. Geyer's lawyer claims the now 13-year-old believed she had to kill her friend or Slender Man "would kill my whole family in three seconds."

On May 31, 2014, Weier and Geyer lured Payton "Bella" Leutner into the woods for a game of hide-and-seek and stabbed her with a knife, apparently in deference to Slender Man. After stabbing her 19 times, the girls left Leutner, who crawled her way to the road and was discovered by a bicyclist.

When detectives interrogated Weier about whether the two really believed Slender Man would kill them and their families if they didn't stab Leutner, the Milwaukee Journal Sentinel reports, Weier told them, "Well, yeah. He's 6 to 14 feet tall, has no face and always wears a red tie. I was really scared. He could kill my whole family in three seconds." (ABC News has that interrogation video.)

The two are reportedly accusing the other of being the mastermind behind the apparently months-in-the-making stabbing plot:

At other times, Weier seemed to comprehend the reality of what occurred, taking some responsibility for the crime, crying when she described Leutner's screams, and saying she wanted to call her mother but Geyser said they couldn't.

Geyser, on the other hand, told a detective Weier was calling most of the shots, and brought up the threat from Slender Man, but also admitted at one point, "I honestly don't know why we did this."

Her interrogator, Waukesha Detective Tom Casey, said he felt Geyser was actually the person most responsible for both plotting, committing and trying to run from the crime.

Detective Michelle Trussoni testified Monday that the girls aborted two planned attacks on Leutner: once while she slept, the other in a park bathroom "so any blood would go down a floor drain."

The preliminary hearing will determine if the girls, both charged by police with attempted first-degree intentional homicide, will be tried in adult or child court. The two were found mentally competent to stand trial last December.

[Image of Geyser, Weier via WITI]