I don't have a link because it's several years old, but another site I frequent had a picture of a GE locomotive piston that exited the engine when it blew the cylinder completely out of the carbody. The cylinder was laying on the ground and the piston had gone through the roof of an adjoining house and got stuck in a wall.
several years ago a lady here was killed when a bush hog blade broke. she was taking her kids to school or picking them up, don't really remember which, and while driving a tractor across the road slung a blade out. it crossed 4 lanes, went thru her windshield, and decapitated her right in front of her kids. your rider/pushmower/etc can do the same thing, this is why no one is allowed outside when i cut. i hit a rock with my X500 and threw it over 50 yard where it blew out the rear window of my Dodge. if that had hit someone even 100 feet away it would have caused serious injury!
If machinery is used and maintained in the manner it was intended then stuff like that doesn't happen any more than people get hit by lightning or win the lottery. Machinery, as a rule, is not dangerous or deadly. Stupidity and ignorance are. Sorry, that's the way I sees it.