Marvin John Heemeyer (October 28, 1951 – June 4, 2004) was an American automobile muffler repair shop owner who demolished numerous buildings with a modified bulldozer in Granby, Colorado, in 2004.

[9] In 1992, Heemeyer purchased two acres (0.8 ha) of land for $42,000 (equivalent to $91,191 in 2023) at auction with plans to lease the property to a friend who intended to build an auto repair shop on the site.

Heemeyer claimed that Cody Docheff had berated him for several minutes afterward out of anger at losing the property; however, no other party present recalled any such interaction.

[11] In 1997, the Docheff family planned to expand their business to include a concrete batch plant and were buying up the land around their current lot, hoping to lease the remaining 23 parcels to small manufacturers.

[1] The commission also suggested that the Docheff family ask if they could purchase Heemeyer's plot to keep the plant away from the hotels and businesses on Route 40.

[5] Despite the deal falling through, the Docheff family pursued their plans to expand their business, and purchased a defunct commercial subdivision opposite Heemeyer's lot.

His campaign was initially successful, with members of the public concerned about potential environmental impacts packing into hearings on the construction proposals.

The clerk referenced Heemeyer's increasingly "exorbitant" demands during negotiations for the sale of his property to the Docheffs, during which he had the land reappraised several times.

[8] Heemeyer tried to appeal the decision, claiming the construction blocked access to his shop,[8] which it never did according to the judge handling his case,[13] a local journalist,[14] and people inspecting aerial photography.

[8][12] Heemeyer was found in contempt of town code in November 2001 by the municipal court, and required to fix the connection issues before he could inhabit or use the property for business purposes again, as well as remove the truck barrel before July 2003.

Knowing the zoning decision was now final, he traveled to California, bought a Komatsu D355A bulldozer in an auction for $16,000 (equivalent to $27,104 in 2023) and had it shipped to Granby in July 2002.

[8] He sold his property for $400,000 (equivalent to $677,595 in 2023)—around ten times the original purchase price—to a waste disposal company in October 2003 and took out a lease for half the building he had previously owned until he had "finished some work.

[1] While no one in Granby saw him, he worked on the bulldozer, illegally constructing living quarters to avoid having to return to his home in Grand Lake, which he saw as a waste of time that could be spent on the dozer.

He was surprised that several men, who had visited the shed late the previous year, had not noticed the modified bulldozer "especially with the 2,000-pound [910 kg] lift fully exposed ... somehow their vision was clouded".

[1] On June 4, 2004, starting at around 2:15 p.m., Heemeyer began his rampage by driving his armored bulldozer through Mountain Park Concrete, owned by the Docheff family.

At the time of the attack, Cody Docheff was at the concrete plant, screening topsoil at the gravel pit, when he got a notification over his radio that there was an explosion at the precast shop.

Cody Docheff, initially believing the dozer to be under remote control, fired a pistol at it and attempted to climb on top, to no effect, before engaging the bulldozer with his own front-end loader, again to no success.

More deputies arrived and began firing on the dozer, attempting to destroy the cameras with gunfire, but were unable to penetrate the three-inch (7.6 cm) bulletproof plastic.

At one point, Heemeyer charged at a firing position occupied by several state troopers, who evacuated mere seconds before he demolished it, with one eyewitness noting that had they taken any longer, they would have been killed.

Undersheriff Glenn Trainer climbed atop the bulldozer and rode it "like a bronc buster, trying to figure out a way to get a bullet inside the dragon".

Heemeyer turned to the Liberty Savings Bank, where he aimed at the corner office where a woman who was a part of the zoning board worked.

Heemeyer next targeted several street fixtures, such as trees and traffic lights, before moving on to the offices of the local newspaper, and in turn the homes of the Thompson family and their workplace.

Heemeyer then fired upon nearby power transformers, with a high risk of igniting the tanks, but struggled to find a good angle.

Members of the State Patrol, however, claim that to the contrary, the governor did consider authorizing an attack, but ultimately decided against it due to the potential collateral damage of a missile strike in the heart of Granby being significantly higher than what Heemeyer could have caused with his bulldozer.

[8] As the bulldozer slowly plowed through the building, one of the previous scrapers was maneuvered onto the sidewalk, blocking it from retreating, after which the operator fled to safety.

[8] About a minute later, at 16:30 MST,[1] one of the SWAT team members, who had swarmed around the machine, reported hearing a single gunshot from inside the cab.

[1][8] Grand County Emergency Management Director Jim Holahan stated that authorities were able to access and remove Heemeyer's body at 2 a.m. the next day, on June 5.

[5][3] His targets included the town hall, the Sky-Hi newspaper office, Gambles General Store, Maple Street Builders, Mountain Parks Electric Co, Liberty Savings Bank, Kopy Kat Graphics, the wall of his former business, the home of a former mayor (in which the mayor's 82-year-old widow then resided), and a hardware store owned by another man Heemeyer named in a lawsuit, as well as a few others.

[24] Cody Docheff stated that "if Heemeyer truly didn't want to hurt anybody, he would have plundered the center of town on the weekend, when most businesses would have been empty".

These ranged from the Docheffs' unwillingness to pay the large sums he requested, the sanitation district's fining of him, and that the town had approved the plant construction.