Marvin John Heemeyer (October 28, 1951 – June 4, 2004) was an American welder and an automobile muffler repair shop owner most known for his rampage with a modified bulldozer which is known as the Killdozer. Outraged over zoning disputes, he armored a Komatsu D355A bulldozer with layers of steel and concrete and used it on June 4, 2004 to demolish the town hall, the former mayor's house, and other buildings in Granby, Colorado. The rampage ended when the bulldozer got stuck in the basement of a Gambles store he was in the process of destroying. Heemeyer then killed himself with a handgun.
Heemeyer had been feuding with Granby officials, particularly over fines for violating city ordinances and a zoning dispute regarding a concrete batch plant constructed opposite his muffler shop.
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 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 13 days before the rampage.
"God built me for this job," Heemeyer said in the first recording. He also said it was God's plan that he not be married or have a family so that he could be in a position to carry out such an attack. "I think God will bless me to get the machine done, to drive it, to do the stuff that I have to do," he said. "God blessed me in advance for the task that I am about to undertake. It is my duty. God has asked me to do this. It's a cross that I am going to carry and I'm carrying it in God's name."
Investigators later found Heemeyer's handwritten list of targets. According to the police, it included the buildings he destroyed, the local Catholic church (which he didn't damage), and the names of various people who had sided against him in past disputes