I usually don't weigh in on this kind of stuff because the media talks it until it is a dead smoking hulk in a hole in the ground but here it is anyway.
There are 3 main problems here. In order:
1. Gun free zones invite murder.
Back during the 'financial crisis' of 2008, a local school district- Lakota schools, consisting of 6 physical schools, terminated 90 - count em NINETY administrators, and 100 teachers and called it good. Now honestly what did any of those 90 'administrators' do beside bring the friggin donuts. If a school can afford to pay 90 admins and 100 teachers that they Don't need, they can pay security people. And how many administrators did they keep? Don't know but it was more than zero. For SIX schools?
People would be offended by armed guards? Bullshit. False argument by the dems who Love when stuff like this happens. It helps them with their gun confiscation agenda. Who would be offended? Students? Hell no. Teachers? hell no. Parents? Too friggin bad if that's true. Suck it up parents who are raising these mal-adjusted assholes that are willing to go out and kill people.
Plano Texas has more guns per capita than probably any place in the US. Murder rate of 0.4 per 100,000 - lowest on the planet.
Get rid of the damn gun free zones.
2. Single mothers. Seriously. Most single mother households have zero ability to raise boys. Adam Lanza, sandy hook, single mother, this kid - sounds like he lived with his grandmother. I recall others similar. Women can't raise boys, Especially Troubled boys, and the women are out of the house working beside. (David Blaine (magician) raised by single mother. Wonderful human being, one of the best on the panet if you get to know him. Not the norm unfortunately.) The kids I knew growing up who were and are whackjobs had single mothers Every single one. And every single one who was in a single mother household was a whackjob. Every single one. Child rearing and raising has to be done a certain way. And this was in the 50's and 60's. Not this FUBAR'd child rearing environment we have today. It doesn't work. It cannot be made to work. You can't drill a hole in a boat and send it out on the water.
3. Kids are being raised to be seriously screwed up. You know what I'm talking about. No one loses, No one can be offended. etc. Few kids can handle real life anymore. Someone gets offended or bullied on social media, they go shoot up a school. Fact. Plus they're given drugs like glasses of water. Ritalin, Adderall, anti-psychotic drugs. These are real and serious problems and the result is you don't get a society full of well balanced people able to handle real life and it's been going on for a good long while.
You can't keep the environment we have and fix it. It is not fixable. The only thing you can do is Deal with it. Start by getting rid of the gun free zones and if a bunch of donut hauling assholes lose their jobs to pay for it, a double win.
Other countries without guns don't have these problems? It is because they also don't have the kind of people we have running around here in the USA. Not a single black person in Russia for example. No border crossers from Honduras either, a country with the highest murder rate on the planet. Not a single person like you find in S. Chicago will you find in any other country in Europe. It's the People. It's the damn people and our society is churning them out like popcorn. It's a wonder we don't have more of these shootings.