Looks like the hanger AND frame broke .... Ouch.
Common cause is the "L" low limit screw misadjusted allowing the derailleur to shift off the largest cog into the spokes.
Another cause is a chain that's too short, so if you are in the big chainring and shift into the big cassette cog, you run out of chain and "SNAP'
What were the circumstances when this happened ? Details ?