After eight people were killed at a Travis Scott concert in Houston late Friday, many of us were left wondering: How did this happen? An expert on crowds explains how too many people packed closely together can become deadly.

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An estimated 50,000 people attended the sold-out 2021 Astroworld Festival at NRG Park to see Travis Scott, whose concerts have a reputation for being raucous.

The Washington Post reviewed dozens of videos from the night to understand how the concert became a mass casualty event, synchronizing video from the audience with a live stream of Scott’s performance published by Apple Music. The videos show a chaotic scene, with concertgoers crying out for help as the show continued, the loud music drowning them out.

The crowd surge victims include a 14-year-old who loved baseball, two friends celebrating a 21st birthday and a 27-year-old attending the concert with his fiancee. Here’s what we know about the victims.

We reached out to Keith Still, a professor of crowd science at the University of Suffolk in Britain, to talk about how these tragedies happen and how they could be prevented.

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