Back in the 50's and 60's religion and the fear of hell was a major force in people's lives in the US. Religion is in major decline in the US and people don't look towards religion as much nowadays. Was religion the missing link in all these modern day mass murders in the US? Would it have made a difference?
It may be part of the equation. Colt started selling the AR-15 in 1964. The AK-47 has been in production since 1949. Columbine was the first really orchestrated school shooting on April 20, 1999. That's 35 years between introduction of the AR-15 and Columbine and 50 years since the introduction of the AK-47. Fascinating how for 35 years there were no mass school shootings with either the AR-15 or AK-47, but as realistic first person shooter computer games advanced realistically in conjunction with reckless prescribing of psychotropic drugs to teens and the school mass shootings started.