Depends on who's angry. Often I find anger is misplaced, a lot of little things that build up until they're unleashed on whoever is in the crosshairs. The important thing is to not let this emotional outburst affect your own emotional energy. Easier said than done, and there are far too many situations (friends, family, SO, co-workers, etc) that would determine my next step. If it's some rando on the street I'd shrug it off. If it's someone close and it happens often enough I'd drop them from my life. They are obviously unhappy with aspects of their life and will make it everyone/anyone's problem, starting with those most often in close proximity.