It feels like a mix of things. Mental health care, for sure. But also media culture as well as violence -- when exposed to it even through movies, television, online, news, video games, etc. -- being something that seems ordinary for a lot of people. Social media plays a part as well, which has been proven in school shootings to the point where schools are now paying to have social media monitored through third parties. The world changed really fast with the advent of technology -- technology is evolving faster than we are -- and I'm not sure that it's particularly good for our species, at least not for all of us.
I grew up watching a lot of TV (latchkey kid) and I maintained that lifestyle for a long time. I was also exposed to violent video games as they were becoming popular when I was much younger. Over five years ago, I got rid of cable and rarely go to movies that aren't chick flicks and haven't played or seen a video game in a very long time. I felt television was unhealthy, both physically and emotionally/mentally. I also realized how desensitized I was to violence and tragedy -- whether on the news or in a show or movie. While TV and movies are fake, they go through a lot of trouble to make it seem real and I think that is confusing for some people and it messes with our minds. It's easy to get involved again and find myself desensitized within a week at most as I have had some television relapses via Amazon Prime. At some point I typically become shocked at how unphased I am by it all and realize it's not healthy then stop. As a normal person without mental illness, all of this is mostly self-awareness, and I know others feel similarly and have given up television and/or the news for similar reasons. I imagine someone with mental health issues may have a different experience, however.
Personally, I think getting "rid" of guns is probably not the answer. This problem is bigger than that. However, I do believe that assault rifles belong in the military. I mean, why would a normal person ever need one? While they would still be available, it would be a lot tougher to get one and you'd have to know the right people.
I don't have the answer. I don't think anyone does.