It happened at a music festival in Houston, a soccer stadium in England, during a hajj pilgrimage in Saudi Arabia, in a Chicago nightclub, and countless other gatherings.
Large crowds surge toward exits, onto playing fields or press up against a stage with such force that people are literally squeezed to death.
But those that went horribly wrong shared some common traits.
People die standing up and those who fall die because the bodies on top of them exert such pressure that breathing becomes impossible.
They were aware that people were dying and they were helpless to save themselves.”
And this month in Indonesia, 131 people were killed when tear gas was fired into a half-locked stadium, triggering a crush at the exits.