When something terrible is happening in a public setting we can experience a kind of shock and mental paralysis that distracts us from a sense of personal responsibility. The problem is that everyone can experience this sense of deindividuation in a crowd. This same sense of losing our sense of self in a crowd has been linked to violent and anti-social behaviours. Remaining self-aware requires some amount of effortful reflection in group situations.
If there’s an emergency situation, presume to be the one who will help or call for help. Be the change you want to see in the world.