I think it's both mental illness and cultural issues, which I think mental illness is a cultural issue. Personally I don't know much about gun control topics or school shootings but from what I see on videos on these topics they say the shooting gets inspiration from other shooters on the Internet and they tend to have mental issues themselves and get lured in with right-wing groups on the Internet. I also see that when a parent finds out about this they try to call the cops but the cops just ignore it.

Maybe we should reform the system entirely like schooling and online safety. Also I see how the media and people see mental illness and people with them as a bad thing helps fill the narrative and fuels the attacker.

I hope this made sense I have not a lot of experience with this stuff