Books have been written on the subject with no clear cut solutions. Evil is a multi faceted problem mankind has been dealing with since Adam and Eve listened to the serpent (as the story goes).
Mainah's post is worth repeating IMO
There's a great, but underutilized, program in the military called Troops to Teachers. It involves helping military personnel transition into a teaching career once they leave the service.
One of the challenges that service members face when trying to obtain a teaching certificate is that requirements vary from state to state. It's tough to work on a Vermont certificate if you're stationed in Texas. States could make it easier for our troops by streamlining certification for them. Ideally they could substitute a current requirement with a security component.
And we're going to have thousands of potential teachers who have unique skills when they leave Afghanistan and Iraq. Not just responding to a school shooting, but identifying problems before they happen.
A large majority of my teachers back in Jr. and Senior H.S. were Vets and were men I looked up to and respected, who treated me like a young grownup (Mr. Baba Louie they called me) and brooked no shinola from the ner-do-wells.
My ex-wife worked in the Dean's office at a couple of our local Middle and Senior H.S.'s, intereacted with and knew most of the "future criminals" (no kidding, that's what these kids called themselves and were proud of the fact) and treated them mostly like young grown-ups and while they usually gave respect back when given it, they were not interested in being there (school or class) in the first place, hated authority, but when expelled would come back to hang around on campus (and thus get charged with trespassing when caught). Guns and knives were not the norm, but they were also not uncommon.
When you can identify the troublemakers (or potential troublemakers), part of the problem is resolved. But it's not always the loudmouthed bangers, be they white, black, latino, asian, etc. you need to worry about nowadays, now is it? It's the dog that doesn't bark more and more, but who somehow, seems to leave clues or "tells" that need to be read by someone who knows how to read the trail and whom the kids trust enough to tell (even tho' squealing can bring about repercussions) and whom the parents might even trust enough to talk to and listen to should they ever decide to be a good parent and care enough about their children's education to interact with their child's teachers. (hard one to resolve that) It may be that a group of teaching Vets, educators who have participated in and know violence, might be in a good position to lessen the impact of future "loner" student violence.
Be they Armed or not.
But as I said, it's a multi-faceted problem.
http://www.wcprc.org/Guns.html These guys blame guns. But there's still some good links within that are worth reading.
Life isn't safe. Bullies have been around forever. Some children can be horribly mean at times. Some kid's parents have no business reproducing. The media loves a good bloody story. In a free society, responsibility starts at home with the individual, but is also reflected from the top down. (Look at our leadership and rage or cry at times)
Criminal activity starts at an early age. This nation has a lot of criminals (which stands to reason since it has a lot of people). The Criminal Justice System doesn't know how to properly deal with them it seems, even after 231+ years of trying. Freedom's like that sometimes. Frustrating in that we've institutionalized our children's formulative years where they get to experience "lockdown" for their own safety. Where have we heard that term used elsewhere in one of our "institutions"? (and aren't THEY safe places to spend a few years?)
Mainah, I'm sure you've heard the old adage, "The true test of intelligence is another who agrees with your point of view". You must be a genius.
(as is 44 Amp)
But all here have given good input and I'm sure all here don't have to worry about their kids as being the problem poster children we're discussing.