And if that kid ending up shooting the other one, and it turned out the police knew of this incident and didn't even investigate, that'd fine, right?
Do you see just a bit of grey area between "ignore" and "arrest"? Hmm?
A parent complained. Fine. The police have a five minute chat with the kid, and maybe, if he sounds completely screwed up, ask for a psych evaluation. End of story.
As presented, he did nothing wrong. This complete bullshit about "terroristic threats" needs to stop now - And "interference of the operation of a school"? Wouldn't that require, I dunno, actually interfering in the operation of a school or something along those lines? Taking a video with your cell phone, crosshairs or not, doesn't do that. Posting that video to YouTube doesn't do that.
Now, in fairness, yes, sometimes we do complain when the authorities look the other way. When James Holmes actually did go to a shrink (several, in fact) prior to his attack, one of whom declared him a threat to the public who outright said he wanted to kill people, and began stockpiling weapons in the six months leading up to Aurora - Not quite the same ballpark as a 15YO playing a game with reality as the background decoration.