The New Yorker has a really interesting article about the dynamics of crowds and how they can turn deadly even when its individual members have no violent intent. Those crushes that have injured and taken the lives of retail employees during Black Friday sales, the odds are no one wanted to kill in those crowds, they just wanted unbelievable savings so big the retailers must be crazy.
This emerging field of crowd studies has found some interesting things about crowds already. Not only do they rarely want to kill, they usually aren't tying to get away from something, as in a panic, which is what conventional wisdom tended to use to account for crowd tragedies that have emerged from time to time, but rather they're trying to get to something, like the Who. And although people do die of tramplings in crowds, people more commonly die standing up, suffocated in a crowd crush that pins them against a wall or a barrier and the other members of the crowd.
The article is a long read, but well worth it. Take some time and learn about something new.