According to the article: The young man's father explained that while playing a video game, “Someone had said something to the effect of 'Oh you're insane, you're crazy, you're messed up in the head,’” he called, “to which he replied 'Oh yeah, I'm real messed up in the head, I'm going to go shoot up a school full of kids and eat their still, beating hearts.’”
My guess is that the authorities want to make absolutely certain the boy was joking before unleashing him on society ... and they probably want to drive the point home that certain subjects do not lend themselves to gallows humor.
If he didn't have inclination to violence before, he might well have by the time he gets out of jail.
unless you are black threatening to riot