Honestly, it kind of annoys me that everyone's first emotional reaction is to jump to gun control and video games. I really think it's a mix of a lot of things. Yes, guns are a big part of our culture. I live in an area where everyone has at least one, and target shooting is a sport. Violence is glorified in the media. The more gory a movie is, the more people love it. Professional wrestlers are worshiped for pounding the crap out of each other.
Yes, most people can handle it. Not everyone goes on shooting rampages. That's when you add mental illness. I have personal experience in how hard finding good treatment can be when you're trying. When I was approved for disability they gave me a check and wished me luck. They didn't give me enough to live off of, so I didn't have Medicare for years because I couldn't afford it. Even if I could have gotten private insurance, I couldn't have afforded that either. A visit to the psychiatrist is triple what a visit to the family doctor is. Medications are pricy. And so, if you're mentally ill, but uninsured, you're screwed.
Then there is all the media coverage. Sometimes when you aren't right in the head, bad attention is still better than no attention at all. They usually end up dead, but hey, they are remembered. The media will talk about nothing except them for days. Everyone will know who their second grade teacher was, because everything about them will be analyzed to death. If you really want to leave your mark on the world, what a better way to do it? It's like a perfect storm kind of thing. Everything is to blame to varying degrees.
While I don't think private citizens should have high powered assault weapons, tighter gun control may not work. In the most recent case, the guns belonged to his mother. She bought them, and for all anyone knows, she was a healthy, stable, law abiding person. The point is, anyone who wants to do this but can't buy their own guns can get them from someone else. I don't think I could buy a gun, but my boyfriend can, and it would still be in the house with me. What would stop me from taking one while he was at work? My mom has several guns, lives nearby, and I have a key to her house. Pass all the tougher laws you want; if I really want to get my hands on one to shoot some people, I will. I don't need to pass a background check, I just need people in my life who can.