Columbine was about two slackers that were bullied by classmates (mental and physical) and disenfranchised/ignored by their own family. They went where they were accepted. they assumed the labels that they were given. Their hate of the school clicks, the establishment, grew and manifested in a desire to act out in the most public way possible. They engaged in a mass shooting with assault weapons.
So 3 things were at play there.
1) Bullying.
2) Absentee parenting.
3) Availability of weapons of mass destruction.
So if any or all of these things were recognized and addressed things would have turned out different. The most important thing would have made it impossible for them to get weapons. Equalizers in their mind.
Nearly 18 years later none of these factors have been addressed...NONE! Just a bunch of lip service, prayers, lies, distractions, and (oh it's not the time to do anything until we have all the facts bullshit)!
It's clear first eliminate weapons! Boom mass shootings averted.
Address bullying!
I don't know what to do about parents that just ignore their kids except hold them accountable for anything the kid does.

To put things into perspective there's about 56,000,000 students in elementary and secondary schools this year in the US. Sure it sucks when there's a school shooting and a loss of life of young people who had their entire futures before them. If it happened to someone I know then I would be highly pissed off and might fly off the handle. But overall it really isn't that big of a problem.

No matter how much money is spent on the problem it won't eliminate it. Heck, teachers routinely assault and rape students in classrooms across the country. Just like school shootings, it doesn't happen every day but it does happen. We sure don't want such things to happen to people we know but when they do we just have to bear it. We won't gain anything by giving up our freedoms for the illusion of being safe.