Accident with angle grinder ( warning )

Sorry to see the injuries. I use to work as an Ironworker and a coworker lost an eye and part his cheekbone when the wheel blew up on a 7 1/2” angle grinder. The wheel apparently was somehow damaged before he began to use it, and as he began to grind it exploded. After that I always test spin a grinder wheel and then put a load on it in a safe direction. To say the least that day at work scared the hell out of me.