Exactly why I NEVER use angle "grinders" with cut-off wheels!!!!!! Bad tool combo! Only cut-off I use is my 14" ridged metal chop saw with a thick blade. It has never ever shattered. Those little skinny hand-held "grinder" (notice the name-sake!!!!!) blade-things are an accident looking for a place to happen (see picture)!
Your hands/arms/body are not rigid enough to prevent binding and torquing of the skinny very brittle little blade in the work.....and it shatters. Avoid angle grinders with thin cut-off blades. They are made for GRINDING and SANDING weld joints/body work smooth..........not cutting-off stock.
Whatever tool you do use............ALWAYS wear safety glasses and a FULL face shield.