A new documentary out this week, called Tread, explores the history of the event. Fifteen years ago, the Colorado mountain town of Granby came under the national spotlight after a disgruntled muffler shop owner drove an armored bulldozer he … In June of 2004, Marvin Heemeyer used an armored bulldozer to conduct a rampage in Granby, Colorado. The incident became known as the "Killdozer rampage." Marvin John Heemeyer (October 28, 1951 – June 4, 2004) was an American welder and an automobile muffler repair shop owner who demolished numerous buildings with a modified bulldozer in Granby, Colorado on June 4, 2004. He damaged many buildings, and ended up dead from a self-inflicted gunshot wound.