Which is Scarier: Slenderman or the American Justice System?

I came late to the story of the two 12-year-old girls in Wisconsin who stabbed their friend 19 times and left her for dead in the woods because they were trying to summon a horror meme called Slenderman. But here's the part that really frightens me:

The 12-year-old suspects were charged as adults with first-degree attempted homicide, and could face up to 60 years in jail. 

CNN confirms:

Two girls, Morgan Geyser and Anissa Weier, were arrested hours after the victim was discovered Saturday, the complaint says. They were being held on preliminary charges of attempted first-degree intentional homicide. Geyser and Weier are being charged as adults and appeared in court Monday. Bail was set for each in the amount of $500,000, Waukesha County District Attorney Brad Schimel said.

How is it even possible to charge a 12-year-old as an adult? Do these people know any 12-year-olds? Does this sound to anybody like the work of an adult criminal?

These girls got lost in a horrific pre-teen fantasy. Yes, they did something terrible. But how does it help anyone to lock two children away for the rest of their lives?

When a crazy 12-year-old does something terrible, that is a tragedy. When a legal system run by supposedly sane adults does something crazy, that is a crime, and we ought not to stand for it.