It's the day after one of the worst school shootings in history. As is typical, there are calls to ban guns entirely, ban "assault weapons" only, strengthen background checks, or in some narrowly defined way, ban men from owning guns since they seem to be the problem. There are the descriptions of the victims, stories of the heroes, and actual videos of the event in progress. There were signs that this guy in particular would be an eventual mass shooter, and there are pleas to lawmakers to do something.
In other words, it is a typical day after a mass shooting. People are horrified, people are outraged, people are fighting over addressing the mechanism of the event (guns) vs addressing the root cause of the event (mental illness most likely). There is data coming out the wazoo on everything gun-related...there has been a massive decline in overall gun violence and gun ownership has dropped to an all-time low while at the same time there has been a sharp rise in mass shootings over the past decade or so and many people are still trying to make sense out of the tough gun laws states vs high rates of gun violence debate.
Sadly, there is no definitive answer about how to prevent school shootings. Much like the answers (or lack thereof) addressing other major societal issues like how to prevent suicide or how to prevent opiod overdoses, there is huge debate over what exactly to do to prevent situations where a lot of people die; in this case school shootings. There are, of course, theories everywhere on the issue (here, here, and here for example) but a serious lack of action in any direction.
IMHO, even though I lean libertarian, I would love to see a free national healthcare system that covers every citizen from head to toe (physical healthcare, mental health care, substance abuse care, dental healthcare, glasses, hearing aids, the works) as a place to start. I think comprehensive mental healthcare--not the "you get to decide what mental healthcare you receive" but a "you are unequivocally mentally ill and will get mental healthcare whether you want it or not" type of care--would go a long way towards fixing many societal issues from homelessness to mass shooters to a prison population in which many of the prisoners are mentally ill to the mentally ill being shot by cops on a fairly regular basis.
Hardening targets is kind of meh in my book since if someone really wants to commit a mass shooting they will find a way to do it (a la the Fort Hood shooting), as is tightening gun background checks (the Las Vegas shooter was a poster child for the kind of person who would easily pass any background check). Mental healthcare, and keeping the mentally ill from accessing weapons, should be the first thing our country works on (with full funding not platitudes!) to address our mass shooter problem.