The world has always been a somewhat sick place where things like this happen. I think it just happens on a larger, more visible scale now.
I'm not a gun guy. You could ban them all as far as I'm concerned. But I realize there are gun people who are responsible gun owners and it wouldn't be right to limit their ability to own and use firearms. And I highly doubt that any level of gun control will ever prevent things like this from happening. It seems serial killers were all the rage in the mid-1900s onward until mass shootings became the outburst of choice for the psychotic.
I don't mean to sound pessimistic, because I'm not. Here's a lecture by Dr. Steven Pinker on how the world is actually getting less violent. The lecture was delivered to the 2015 Nobel Peace Prize Forum, which I am proud to say that my alma mater--tiny Augsburg College in Minneapolis--was instrumental in establishing about a decade ago. The lecture is about an hour long, so kick back with some popcorn and a Dr. Pepper.
[video=youtube;s3wUIZc5a1c]https://www.youtube.com/watch?v=s3wUIZc5a1c[/video]