The Slenderman Stabbing

"ARE THOSE WHO WE SHOULD BE MOST SCARED OF ... THE ONES WE KEEP CLOSEST ?"

A 12 year old girl dead. Killed by her two best friends. What could have happened to cause this? What could have twisted them to do this? Who could have twisted them to commit murder? Only one thing is capable of this ... Slenderman. Based on a true story.