The first kill was the guy original beside the tractor, not the guy who ran/jogged over to it. He was the second. The second guy can be seen unwrapping something, rather feverously, just before the hammer falls on him. The tractor is hot, you can see a bright vertical stripe on it's left side, which would be the exhaust stack, and at the rear you can see the rear axel of the tractor is also quite warm. The engine is shielded from view for the most part.