IMO, he is old enough to fix his own problems. Don't call mom and ask her to fix it, skip school and take the gun home your self, or shut your mouth, play the odds of anyone breaking into your truck, go to school and take the shotgun home after classes are over.
I agree that the punishment is extreme, and I would imagine that any decent attorney would beat the criminal charges on the "knowingly and intentionally" elements of the crime.
On a side note, what 17 or 18 year old doesn't have a cell phone today? He couldn't phone a friend or family member from a private location to ask for some help?
Be safe.