WAUKESHA, Wisconsin - Two 12-year-old girls from Waukesha, Wisconsin, are in a juvenile detention center tonight. They are charged with attempting to kill another 12-year-old girl, who was stabbed Saturday 19 times.
On Tuesday, an attorney for one of the accused said she shows signs of mental illness.
The brutality of the crime is hard to square with the ages of the accused. The two 12-year-olds now facing adult charges of attempted homicide.
CBS News has hidden their identities because of their age.
Police say the suspects told them they assaulted their friend in a local park after months of planning, inspired by a website known for horror stories.
Russell Jack is the Waukesha chief of police.
From what he knows of the case did the suspects have difficulty distinguishing fact from fiction?
"It appears that based on their Internet usage, the websites that they were on, that they had some difficulty with distinguishing that and thus they carried out these acts," Jack said.
According to the criminal complaint, the girls wanted to kill their friend as an act of devotion to a horror character called Slenderman, whose exploits are distributed on a website called Creepypasta.
Someone identified as the website's administrator wrote "... only a small minority of people (mostly newcomers) on the (site)... truly believe what they read here," adding "Something like this was bound to happen considering the size of the Creepypasta community."
Slenderman videos have millions of views on YouTube. There's even a video game.
"For a lot of people, the real world and the Internet world are essentially the same thing," said Lindsey Turrentine with the technology website CNET.
She says Slenderman stories are the downside of going viral.
"They are very short, they're very easy to copy and paste and spread, and that's part of what has helped it move around in this insidious fashion," she said.
Defense attorneys in this case say they will attempt to have it moved to juvenile court, while the 12-year-old victim in this episode is described Tuesday night in stable condition.