We've seen it happen at soccer games, concerts and other large scale events like the Halloween festival in Seoul, South Korea.
Crowd surges can sweep up revelers, causing major injuries and even deaths -- more than 150 people were killed in Seoul alone. How do people die in situations like this?
The fire chief said what tends to happen in these large crowds is that something triggers a wave, like someone falling or a fight. This wave then creates a large movement of people to the point where they are crushed against each other or a building, and the deaths usually occur by compressive asphyxia.
What can you do before you go into a crowd? Is there a way to prevent getting caught up in a surge while also enjoying the event you're at?
The best thing you can do is to understand the event, the chief emphasized.