One time I was getting some steel collected by a pair of scrap guys. I had to lop the back off a chassis because I wanted to keep the back half. They lifted the chassis off the ground with the tilt tray for me, and I grabbed the grinder. I was doing the cut like you would with a chainsaw: a shallow cut at the bottom, followed by cutting the full depth from the top, so your saw doesn't jam and the branch doesn't split; so I cut one rail, no worries as it was supported by the other rail. Then I cut the bottom of the second rail with the grinder, then started at the top. As I was getting to the end of the cut and was preparing for the chassis to drop to the ground, genius scrap metal guy tries to be helpful and grabs the end of the chassis to support it. Rather than being smart and holding it at an angle so I can finish my cut in safety, he dragged it back up to level, and overbaked it, jamming the grinder disc hardcore and causing it to explode.
I was lucky and the bits of grinder disc missed all flesh, only hit my full face mask, but the guy copped an earful from me.