A Mass Shooting Over...A Video Game

So a guy lost at a video game today and decided to shoot everyone in the gaming lounge.  Fortunately he's dead which is an improvement to the gene pool but the question of why still remains.  Not the why did he specifically do it, but the why are there so many mass shooters over the past decade or two when, for many decades previous to that, when nearly everyone owned guns, there was barely a concept of mass shootings.  I have no answers as to the cause or the how to fix it (other than arming myself and staying away from people as much as possible) but some interesting discussion on the topic can be found here (read the comments too), here, and here.