Well yeah, but also there was very little buildup to him becoming a school shooter. Things like that take years of severe mental illness and ostracism for someone to be driven to that point. Sure, Tyler was bullied and what Monty did to him was nothing short of life-shattering, but Tyler just seems like a lonely nerd for much of his screentime up to that point. It would’ve been more likely that he tried to kill the jocks that were responsible, not… an entire room full of innocent people.
Simply shooting a gun in the forest with an edgy friend isn’t really enough buildup, and his little gun cache at the end of season 1 came right the f**k out of nowhere.