So, where were his parents? You mention the school’s responsibilities- what did the school do? I had read anywhere that he was ganged up on by twenty bullies - so why weren’t the police involved?
From what I’ve seen so far, the psycho didn’t shoot bullies - he shot the principal and bystanders.
Broken brain, likely from a broken home.
No one said he was physically ganged up on, so police involvement hasn’t been discussed so far as I know. His parents are married and both have good reputations in the town, with stable employment.
No one is actually defending what he did, but I do think schools and parents should try like heck to discipline youngsters who bully. No one has to like them or approve of them or sympathize, but, until they do something, leave them alone and maybe they’ll stay calm. Then everyone wins.