From a great New Yorker piece from 2011 on crowd psychology:

The origins of the term Black Friday are obscure. Some think that it was first used by the police in Philadelphia to describe the snarled traffic and sidewalk hassles that came with the day after Thanksgiving and crowds arriving for the city’s annual Army-Navy game. Others have defined Black Friday as the day that merchants’ balance sheets crossed over into the black. Either way, it is now a de-facto national shopping holiday. On TV, images of people racing through the aisles of stores for sale-priced items, in a sort of American Pamplona, have become as much a part of the day after Thanksgiving as leftovers. Shoppers get discounts, programmers get some lively content for a slow news day, and retailers get free publicity: a good deal for everyone, except for the clerks who have to work that day, breaking up fights among shoppers and cleaning up the mess left behind.

There had been injuries on previous Black Fridays, but no one had ever died before Jdimytai Damour went down in the Valley Stream Wal-Mart. His death, and the “Wal-Mart Stampede” that caused it, was the lead story on news channels across the country that evening, and it provoked a vast outcry of horror. In days of commentary that followed, the crowd was widely vilified. The tone of much of the reaction was captured by a letter writer to the New York Post, who blamed “the animals (you know who you are) who stampeded that poor man at Wal-Mart on Black Friday: You are a perfect example of the depraved decadence of society today.”
To be clear: we are all animals. Rich, poor, black, white, Latino, Chinese, Indian, —every human on every continent is an animal. Whatever humans are orbiting in space are animals too.
We like to think of ourselves as these evolved beings with smartphones and clothing, the smartest creatures on Earth. What we usually don’t bother to acknowledge our animal instincts. Our survival instincts for food and shelter and sleep. The fact that we make many day-to-day decisions in life based on irrational reasons.
Underneath our higher brain lies the lizard brain, the emotional brain we can’t control.
I think it’s reckless for any business to have events without proper understanding of crowd psychology and without implementing proper measures to avoid bullshit like stampedes and looting.