Marvin Heemeyer

For visibility, the bulldozer was fitted with several video cameras linked to two monitors mounted on the vehicle's dashboard. The cameras were protected on the outside by 3-inch (76 mm) shields of clear bulletproof lexan. Compressed-air nozzles were fitted to blow dust away from the video cameras. Onboard fans and an air conditioner were used to keep Heemeyer cool while driving. He had made three gun-ports, fitted for a .50 caliber rifle, a .308 semi-automatic rifle, and a .22LR rifle, all fitted with a one-half-inch-thick (1.3 cm) steel plate. Heemeyer apparently had no intention of leaving the cabin once he entered it. Authorities initially speculated that he may have used a homemade crane – found in his garage – to lower the armor hull over the dozer and himself. "Once he tipped that lid shut, he knew he wasn't getting out," Daly said. Investigators searched the garage where they believed that Heemeyer built the vehicle and found cement and armor steel.

At this point, local authorities and the Colorado State Patrol feared they were running out of options in terms of firepower, and that Heemeyer would soon turn against civilians in Granby. Governor Bill Owens allegedly considered authorizing the National Guard to use either an Apache attack helicopter equipped with a Hellfire missile or a two-man fire team equipped with a Javelin anti-tank missile to destroy the bulldozer. This was quickly deemed unnecessary when Heemeyer became trapped in the basement of a Gambles hardware store. As late as 2011, Governor Owens's staff still vehemently denied considering such a course of action, but since then members of the State Patrol revealed that, to the contrary, the governor did consider authorizing an attack but ultimately decided against it due to the potential for collateral damage of a missile strike in the heart of Granby being significantly higher than what Heemeyer could have caused with his bulldozer.

On April 19, 2005, the town announced plans to scrap Heemeyer's bulldozer. The plan involved dispersing individual pieces to many separate scrap yards to prevent souvenir-taking.

Heemeyer had feuded with Granby town officials, particularly over fines for violating city health ordinances when he chose to dump sewage from his business instead of installing a proper septic tank. His feud came to a head on June 4, 2004. Over about eighteen months Heemeyer had secretly modified a Komatsu D355A bulldozer by adding layers of steel and concrete, intended to serve as armor. He used this to demolish the Granby town hall, the former mayor's house, and several other buildings. Heemeyer's rampage concluded with his suicide, after his bulldozer became trapped in the basement of a hardware store he had been in the process of destroying.

On June 4, 2004, Heemeyer drove his armored bulldozer through the wall of his former business, the concrete plant, the town hall, the office of the local newspaper that editorialized against him, the home of a former mayor (in which the mayor's widow then resided), and a hardware store owned by another man Heemeyer named in a lawsuit, as well as a few others. Heemeyer leased his business to a trash company and sold the property several months before the rampage.

In addition to writings that he left on the wall of his shed, Heemeyer recorded a number of audio tapes explaining his motivation for the attack. He mailed these to his brother in South Dakota shortly before stepping into his bulldozer. Heemeyer's brother turned the tapes over to the Federal Bureau of Investigation (FBI), who in turn sent them to the Grand County Sheriff's Department. The tapes were released by the Grand County Sheriff's Office on August 31, 2004. The tapes are about 2.5 hours in length. The first recording was made on April 13, 2004. The last recording was made thirteen days before the rampage on May 22.

In 2001, Granby's zoning commission and trustees approved the construction of the concrete plant. Heemeyer attempted to appeal the decision but was unsuccessful. It was claimed by Heemeyer that the construction blocked access to his shop. He was subsequently fined $2,500 by the town council and a city judge for various violations, including "not being hooked up to the sewer line;" he had initially been unable to connect to the new sewer line as the line ran some sixty feet away from his property and the city expected him to pay the nearly $80,000 cost of laying the connector, and after the concrete plant was built the city council denied him the easement necessary to join to the new line underneath the plant.

In 1992, Heemeyer purchased 2 acres (0.8 ha) of land from the Resolution Trust Corporation, the federal agency organized to handle the assets of failed savings and loan associations. He purchased the land for $42,000 to build a muffler shop and subsequently agreed to sell the land to Cody Docheff to build a concrete batch plant, Mountain Park Concrete. The agreed price was $250,000. According to Susan Docheff, Heemeyer changed his mind and increased the price to $375,000, and later demanded a deal worth approximately $1 million. Some believed that this negotiation happened before the rezoning proposal was heard by the town council.

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.

Marvin Heemeyer was born on October 28, 1951 in South Dakota and lived in Grand Lake, Colorado, about 16 miles (26 km) away from Granby. According to a neighbor, Heemeyer moved to town more than ten years before the incident. His friends stated that he had no relatives in the Granby–Grand Lake area.