A terrifying and interesting story that I first heard of from the Podcast “Last Podcast on the Left”, specifically episode 511 The Biggest Ahole of the 20th century. While they do a bit of a deeper dive, the linked wikipedia article goes into a lot of detail as well.

It’s really crazy to hear of Kehoe’s motivations. It seems he had a large ego, thought highly of himself (he wore a goddamn suit while farming), and had a strong and warped idea of right and wrong. He was also intelligent, and was very successful in planning this horrible massacre. He improvised a shrapnel bomb by loading the back of his truck with explosives and scrap, for example. I really can’t believe I hadn’t heard of this sooner.