I found about him on the Something Awful forums, where they presented him as some kind of folk hero who was fighting against the man and AFAIK they still have Killdozer emoji.
He was actually a libertarian asshole who thought it was government tyranny that he couldn't keep emptying human waste into an old concrete truck barrel. He would've gotten a ton of money for his property that was going to have a concrete plant built on it, but he refused.
It was really just luck that he didn't kill anyone, he ran his dozer into a library where a bunch of children had gathered, but they were evacuated just in time.
I dunno why I'm talking about this now fairly obscure piece of Internet lore except I randomly thought of him a few days ago and realized it was almost exactly 20 years ago (). I guess it's also a good example of how telling a story selectively can change its perception, which is relevant with Tiny Man Square having its anniversary too.
Also there was an indie documentary called Tread released at the 2019 SxSW Film Festival, it includes historic video of the event mixed with live re-enactments, plus clips of Heemeyer's audio tapes and interviews with the people he was after.
It was posted to YouTube's "free with ads" movie section a few years ago and remains free to this day, link to watch the whole thing (it's about 1h28m).