Children express their anger impulsively and, well, childishly all of the time. Screaming “I’m gonna kill you” to your brother who just ate the last cookie or a close friend who just beat you in your favorite video game is considered normal despite the phrase’s literal meaning. But in June, two 12-year-old girls from Waukesha, Wis., were not joking when they stabbed their friend 19 times and left her for dead as a way to please a mythological creature. Now, one of the girls has been found unfit to stand trial, according to her attorney.

Both girls will be charged as adults in Judge Michael Boren’s court. The made-up Internet character Slender Man told them to do it, the girls pleaded when they were found out. One of the girl's state public defenders, Joseph Smith Jr., said she was unfit based on a psychologist’s evaluation in July and treatment in August. Parents stood stoically and some cried in the courtroom as the tween girls dressed in prison jumpsuits and shackles held with a $500,000 bond each. If convicted, both girls could face up to 60 years in prison, according to The Associated Press.

"I recognize their young ages, but it's still unbelievable," Court Commissioner Thomas Pieper said during one of the girls' initial court appearances Monday. The police reportedly said she “stabbed the victim more than a dozen times, heard voices, and believed she could communicate with Slender Man and other fictional characters.”

What makes children murder? Could these girls have been experiencing the early stages of psychosis, schizophrenia, or another state-altering mental illness? We like to think that children are innocent and remain that way until they make their way through rebellious temptation they find sin and in some cases enjoy it. According to Parents magazine, it’s normal for 12-year-olds to experiment with smoking and alcohol as a consequence of peer pressure. Was that a motivating key to this monstrous attack?

One of the girls told a detective they were trying to become “proxies” of Slender Man, a mythological demonic character they learned of on Creepy Pasta Wiki, a website dedicated to horror stories and legends. The girls invited their friend and later the victim to a slumber part on Friday evening and decided on murdering her at night so they didn’t have to look her in the eyes, one girl told police. Then they planned on running away to the demon’s mansion in Nicolet National Forest afterward but were unsuccessful. After the victim was stabbed and left alone to die in the woods, she crawled her way to the side of the road where a bicyclist found her and called the police. The student recovered physically and returned to school this fall with horrifically traumatizing summer memories.

Why are we so shocked by children who murder before they hit their teenage years? Somehow the prepubescent age has become an angelic, untouchably fragile, and incapable of murder. Children who murder are considered “monsters” and many will question if it’s the parents fault, the school, the television, or if they were simply just bad seeds, born from something evil. Did the Internet pull these two 12-year-old girls into the dark reproach and turn them into capable murderers? Why do children kill?

Ten years ago, there were 16,137 murders committed in one year and 10 years before that there were 23,326 murders, according to the Bureau of Justice Statistics’ Homicide Trends in the US. The number of children murdering under the age of 14 was at its highest in 1993 and 10 years later fell to its lowest in 2003 and continued to steadily fall in the years following. Yet they still kill and follow the same exact trend as the adult murder rates peak, drop, and plateau.

Invariably, there will always be murder, victimization, and cyclical patterns and acts of random violence. But for some reason, children remain the labeled monsters, while the right of passage through puberty magically turns the once deceivingly innocent young monster into another average murderous adult.