ellen gabler is a reporter at "the milwaukee journal sentinel."as followed this case closely. >> the thing that was the most surprising and shocking to me was how planned out this whole thing was. >> reporter: the portrait they paint even before those woods is chilling. a plot they tell police that was in the works for months. >> you can't believe this is actually 12-year-olds, especially 12-year-old girls. >> reporter: they tell police they committed this crime in part out of their devotion to a character they discovered on the internet. slender man. a tall, faceless, mysterious figure. a fictional character who lurks in the background, sometimes peering over the shoulders of children. the story of slender man changing, evolving all the time with help from fans all over the world adding to the story online giving this fictional character new life every day. you have said that slender man is the bogeyman of this digital generation. >> he is. the thing that we fear that we don't actually encounter. right? so we check our -- we check under our beds