That chart confirms what I recall during the days when President Reagan was in office and America was at its height, second only to the Calvin Coolidge era. Mass shootings virtually came to an end during his inspired leadership. And things are now out of hand, just as they've always been during the DemonRAT's reign of terror. The notable school shootings peak during the KKKlinton and obama/holder regimes. And I vividly remember that things were awfully bad when Klansman Karter and his incompetent buffoons grasped power for a few years in the 1970s.
And need it be said that all political assassinations and attempts of the past 150 years have been perpetrated by leftists. Every...single...one.