On June 4, 2004, Marvin Heemeyer used a homemade armored bulldozer to destroy 13 buildings in Granby, Colorado, during a 90-minute rampage that caused $7 million in damage. Heemeyer’s modified Komatsu bulldozer—later dubbed the “Killdozer”—came loaded with steel armor plating, cameras, and gun ports, making it almost impossible to stop. It all started with what seemed like a regular business dispute over zoning and sewer connections. Heemeyer, who ran a muffler shop, felt local government decisions had boxed him in. Over a year and a half, he quietly turned his bulldozer into an armored juggernaut and mapped out his attack...