I'd really like to see a study about what I'll call "fevers" (for lack of a better term) that take over this country for periods of time that may be as short as a few years, or may run decades in length, because my personal opinion is that we are in the midst of one of those "fevers" right now, one that involves mass shootings in schools or work places, primarily.
Think about it a bit. There were a few decades in this country where train robberies were a thing. They were a frequent occurrence. When was the last time you heard of someone boarding a train, robbing it, and making their getaway?
Lynchings. How many people in this country, primarily black men, were drug out of a jail and lynched by an angry mob after being accused of a crime? When was the last time you saw that?
Did you know that sneaking into homes and murdering entire families in their beds with an axe was a thing in this country. There was a decade or two in the late 1800's and early 1900's where this was a serious problem in the country. How often do you hear about that happening today?
I grew up in the age of airplane hijackings. I think there was maybe a ten year stretch or so where we were averaging something like one hijacking a week, or some ridiculous figure. Then, as quickly as it became a thing, it no longer became a thing, and that was long before the increased airport security that followed 9/11.
We're living in the age of school shootings, and it's cousin, workplace shootings. I personally believe such events will become passe in the minds of psychopaths, and they will move on to some other fever that catches their attention.