Such a complex issue. The ONLY thing I disagree with is when people refuse to be open to discussion about what to do. I am in schools all the time. Today I was consulting with a high school principal and assistant principal about a cadre of students who are troubled and disengaged. Every HS in America has students with mental health challenges and many of these youth have unstable home situations and some have access to guns (btw, the consultation today was in New Hampshire in an area where gun ownership is common and highly valued). The interesting thing is actually that the vast majority of teens who might meet many of the risk indicators (MH issues, gun access, unstable homes, school disengagement, relationship problems...) will actually NOT become school shooters. My point is that fine tuning the assessment of risk factors and "protective" factors (i.e. factors that mitigate risk) will not produce an iron clad profile, but may serve to get us closer to identifying those most likely to commit these crimes. That said, identifying how to effectively intervene when school/community/family culture is invested in reactive "discipline" as opposed to proactive support will be an additional monumental challenge.
All I can say is that I hope there are only a dwindling few still out there who are closed to a conversation that COULD include measures that reframe gun ownership rights and gun owner obligations. But... the solution, if there is one, needs to be multi-pronged.