Welding, Marvin Heemeyer, Killdozer, Granby,

What would cause a seemingly ordinary man to secretly fortify a bulldozer until it was bulletproof and explosive-resistant, then drive it down to city hall and level it, while destroying local businesses and pancaking police cruisers along the way?

In the spring of 2024, I moved to Grand County Colorado for a few months to embark on a research project for my first non-fiction book about the unbelievable true story of Marvin Heemeyer and his giant, weaponized bulldozer.

In 2004, the media ran wild with this story, sensationalizing it by referring to the machine as “The Killdozer.”

Hauntingly, a note Marvin left behind read:

  • What caused a man, who his friends referred to as a gentle giant, to destroy a small town in Colorado in a homemade tank?

  • How was a lone welder able to create a machine that couldn’t be stopped by police, civilians, or other massive heavy machinery?

  • And perhaps, most importantly, are we all only one bad day away from going on a rampage ourselves?

There is more to the story than meets the eye (much more!), and I can’t wait to share it with all of you! You can sign up for updates here.

Because of the sensitive nature of this story, I will be donating 100% of any profits from this book to charities (primarily charities chosen by folks who help me with my project by sharing their stories and memories, and ones that benefit Grand County, Colorado communities)

Welding, Marvin Heemeyer, Killdozer, Granby,

I fell down the rabbit hole of this story a couple years ago. I had never heard of it before, until an offhand comment by a friend sent me scurrying to research more about it.  In case you aren’t familiar with it, below I’ll share a little about this wild story. 

But be warned, like me, you might get hooked.

Marvin Heemeyer was the owner of several muffler repair shops in Colorado, including one in Granby, a little town nestled in the mountains with a population of about 1,700 people at the time of the incident.  Over the course of a decade, a bitter feud was brewing between Marvin and some other local business owners.  Further fueled by small town politics and lawsuits, the fighting reached a fever pitch, where Marvin felt his business had been destroyed by others.  So what would he do?

You know how sometimes someone “snaps”?  And they grab a gun, storm over to their neighbor’s house, and in a fit of uncharacteristic insanity, shoot someone? Well, perhaps Marvin snapped…but rather than do something rash, he slowly and methodically plotted his plan – for revenge or for justice, it’s up to us to decide.

A masterful welder from his many years of repairing vehicles and building customizations for snowmobiles, Marvin began to utilize his skills for a secret project.  Slowly, over the course of a year and a half, he modified an enormous Komatsu D355A bulldozer, which weighs in at nearly 50 tons (pre-armor).  Using steel plates and concrete, and toiling for months in a storage building, Marvin created his engineering marvel, the likes of which had never been seen before.  As his project neared completion, so too did his end-of-life planning – he’d given away his home, his money, and his assets.  All that was left was him and his dozer, which he called the MK Tank.

June 4, 2004 would become a day that would live in infamy, as Marvin climbed inside and began a several hour-long rampage where he destroyed the neighboring concrete plant (which had been the main source of his long-festering anger), the town hall and police headquarters, the bank, the local newspaper, the house of the town’s former mayor, a hardware store, parked cars, and more.  It was an extremely targeted attack – Marvin had a personal problem with someone at each building he destroyed.   Neighboring buildings were left completely unscathed while others were razed to the ground, as if a tornado had come through.

The machine itself is beyond comprehension.  Among all the metal and concrete, welded together so meticulously there was no apparent entryway when looking at in from the outside, Marvin had outfitted the dozer with small view ports and cameras to see out.  He even went so far as to install tiny hoses connected to compressed air, so he could blow dust away from the bulletproof glass over the cameras because he knew there his vision would become obstructed from the falling debris of the buildings he planned to destroy.  He had, seemingly, thought of everything, and built his machine accordingly.  It was impervious to the many methods police and members of the community used in vain attempts to stop it, from high-powered ammunition, oxygen in an attempt to hyper-rev the engine, explosives dropped into the exhaust or discharged against its side, and massive heavy machinery to combat it like gigantic battle bots. 

The footage from the rampage is incredible and looks like something out of a movie. You can watch Marvin navigate his monstrous homemade tank right into huge buildings, with walls of bricks raining down on the dozer.  But it was built so sturdily that even after being buried by a collapsed building, it would simply back up, its treads squeaking and squealing, then lurch forward again for another hit. 

No one got hurt or killed (with the exception of Marvin, who took his own life at the end), but he caused millions of dollars in property damage, only targeting those he perceived to have had a hand in destroying his business. 

Marvin left behind three cassette tapes where he shared some of his story. He recorded them only a few weeks before the rampage. You would think someone in that frame of mind would sound unhinged and extremely angry, but shockingly, he wasn’t like that at all. He seemed frank and straightforward as he reported incidents, dates, and names of people, documenting a decade of slights and wrongs he claimed against him. By recording these tapes, Marvin proved that he wanted to share his story. Numerous times, he genuinely sounded sad about what was about to happen, as if he himself didn’t actually want to do it but was compelled on by some outside force.  At one point, he speculates on if something could crop up that would change his mind and cause him to dismantle his tank.  “Didn’t happen folks.  It didn’t happen.  Why didn’t it happen!?  You had a whole winter to have something happen good to Marv Heemeyer,” he says, on one of his tapes, his voice taking on a pleading, almost desperate tone, before settling back down and getting serious again.  “It didn’t happen.  So here I am, back there, doing what I have to do…I’m building the MK Tank…

“There’s just so many things that I’ve hoped for that I wouldn’t have to do this…” he says during another part of the recordings.

He was so convinced that ‘teaching the people in this town a lesson’ was the right thing to do that he was ready to give up his own life to prove his point. Because once he climbed inside the dozer, he knew he’d never get out of it. 

There is a great documentary about this incident called Tread, which you can watch for free on YouTube (I’ll link it below).  My foray into the lore of Marvin Heemeyer started there before I spiraled, watching and reading everything I could find about the incident.  Once I started down this path, I got addicted.  The more I learned, the more questions I had…because the story truly gets more and more insane! 

After the rampage, Marvin became a polarizing figure.  A large faction of people in certain circles view him as an American folk-hero, the ultimate example of fighting back against corruption.  Others see him as a villain – a mentally unstable intimidator who chose to endanger the lives of many over petty revenge.  Where does the truth lie?

As I began interviewing people who knew him, I wondered what the perception would be.  I was surprised when certain themes started to emerge.  Phrases like “gentle giant”, “great heart”, and “good guy” kept coming up.  Among local snowmobilers, Marvin was a hero who saved several men during an avalanche one winter.  Even some of the people who were directly affected don’t seem to hold a grudge against him, speculating that he was pushed too far.  I am completely fascinated with what caused a seemingly normal and well-liked man to do something so drastic that ultimately cost him his life. 

I’m not looking to glorify what Marvin did as I begin this project about his life. I’m just interested in uncovering the backstory of what exactly led to such a wild event. So far, everything out there about this story really focuses on the incident itself, and Marvin seems to get sort of lost along the way.  He was a real person.  June 4, 2004 was one day in his life – what about the other 52 years he had lived?  He had grown up in South Dakota, was a son and a brother, served in the Airforce, owned and operated a variety of businesses, was an avid outdoorsman, and had a big group of friends.  I want to know his story from all angles.

If you are interested in learning more, you can check out this great documentary called Tread (linked on this page).  But what happened that day in Granby, Colorado, and what led up to it, can’t be covered in an hour and a half.  There are so many twists and turns. And the deeper I get into it, the more intriguing it gets.

The day of the rampage was one of the closest incidents the US government has ever come to calling in an air strike on one of its own citizens. I’m working to uncover the truth about one of the wildest true crime cases that has ever happened

Vengeance. Corruption. Ingenuity. Danger. Patriotism. Folk-hero or villain?

Follow along with me on my adventures to and from Colorado as I research, while I work to uncover never-before-told stories, long-held secrets, and the truth behind the ‘Killdozer’ rampage.

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