Who is guilty of the Slenderman horror?

It was with horror I read an article about two 12 year old girls who plotted to murder a friend for a fictional internet horror character call Slenderman.  A being somehow created through viral internet rumour who is malevolent and fictionally kills children.  It makes me wonder how on earth such a concept can be allowed to run riot in the world.  Small children are easily influenced and do not understand right from wrong or what is fictional and what is real. This character has been allowed to snowball into a scary creature, to the extent these girls thought he was real and by killing a classmate they would curry favour with him. They just didn't have a grip on reality and are going to be tried as adults. Their victim was stabbed 19 times, she did not die and it must of been with superhuman effort she crawled out of a wood to a track and was discovered by a cyclist.  She is currently in hospital and stable.  The attempted murders have been bailed for $500,000 each. This took place in a wood in Wakuesha, Wisconsin. 

However, I cannot help think the creator of this character is also part to blame.  If they had weaved a story early on how Slender man liked to stamp on snails and snatch doughnuts from children with his biggest kick coming from leaving his tag on homework books then there would be little in the way of moving deeper into his malevolence.  The creator of this character should of had some small incite into how children think.  They are in my mind equally liable and particularly so would be those who hide behind a cloak of anonymity embellishing his life history with worse deeds. The imagination of these little girls was wild on what they had read from the internet, they are not responsible for this action but at the same time they are. They will now never get the chance to lead a normal life and because of this single action in their lives be forever tainted as evil girls.

The sad thing is, this is a story to learn from and to act by changing the laws and protect children. I wonder if this will happen?