I hear what you're saying. The one thing I disagree with you is that there is a LOT of "noise" "drama" whatever you want to call it with kids in school these days. So much worse now with everyone yakking on social media. Most if not all is hearsay.
Hearsay/rumers do not get you search warrants or hold up in court.
If these parents were called and talked to by the school and refused to take the kid home and after the "talk" this kid went berserk well the parents could have stopped this by taking the kid home, they also could have searched the kids locker,bag etc and seen if he had the gun and STOPPED it.
The kid should not have had unlimited access to this firearm, This we can agree on.
I taught my kids from a very early age the fundamentals of gun safety, they could handle them ONLY in my presence and then they were locked up. When they asked to see them I accommodated that and they were to show the safety they were being taught in handling ANY firearm.
We went shooting/hunting and used the firearms.
I personally think every kid should take a Hunters safety course EVEN if you do not hunt. They go through firearm safety which I think is very beneficial. Even though I'm teaching them I know from my own self you learn other perspectives from other teachers EVEN learning the same stuff.