Is the high school junior of legal age to possess a rifle? HS Junior’s are normally 16 or 17 years old. If he is below the age of legal gun possession, the police have a duty to confiscate weapons they see that are illegally in his possession.
The kid’s “joke” was an implied threat that he was going to shoot up the school on a particular date, while holding the means in his hands. That was moronic at 12 years old, much less 18+. If a parent is supervising and guiding his path to responsible gun ownership, they have not done a proper job teaching him common sense and legal aspects. His parents, not the State, should deprive the kid of access to any sort of weapons until he matures and heals.
In most states this is open-and-shut Making a Terroristic Threat. Don’t do the crime if you can’t do the time. Don’t know if it’s a felony but I’ll bet it is.