In Seattle in 2001, a 26-year-old woman who had recently ended a relationship held up traffic for a little too long as she considered the implications of leaping to her death. As motorists began to back-up on the bridge and become irate, they started yelling “Jump, bitch, jump!” until she did.
Cases like this aren’t unusual.
When people feel anonymous and fade into a larger group, they are capable of doing things that would normally horrify them. You Are Not So Smart explores deindividuation.