I really guess its a thing on values in culture. It's becoming worse, that is. :/
Was never like that in my parents' times.
I wouldn't say values are getting worse. I mean, everyone's values are worse to everyone else because you measure things by your own.
But It's more like... the things that make doing stuff like that worthwhile is more of a thing? I mean, with global news and the internet you could go and shoot a bunch of people and within hours most of the English-speaking world would know about you.
Then again, I have a hard time believing all these shooters just had a pathological need for attention and figured killing people was the way to get it. I think media is a contributing factor but....I think societal pressures and perhaps people's inability to deal with stressors is the more likely cause. Kids were bullied, perhaps even more brutally, 30 years ago than today. People lost jobs in larger numbers. Wages didn't suck as bad then as they do now but.....politics was still as volatile and perhaps only slightly less polarizing. (I mean, you want to talk polarizing political discourse? Read the shit politicians said about each other and their agendas during the Civil War-era! The kind of shit you'd be shamed out of politics today for saying today.) We can't even claim there's more alarmist propaganda today than previously; WW2 puts paid to that.
So I dunno. Like with most complex problems, it's a variety of factors most likely. But where to start, to begin chipping away at the problem? Gun control isn't a feasible answer, because supporters would rather the status quo continues than even experiment to see what most restrictive gun control might accomplish. And again, it's a bandaid to the larger contributors to the problem.