On 24 July 2010, 21 people died at the 2010 Love Parade electronic dance music festival in Duisburg, North Rhine-Westphalia, Germany.
This video attempts to explain why this happened.
According to Wikipedia:
The Love Parade was a popular and free-access festival and parade that originated in 1989 in Berlin. The parade featured stages, but had floats with music, DJs and dancers moving through the audience. The Love Parade in Duisburg was the first edition of the festival that was organised in a closed-off area.
The festival was staged on the area of a former freight station.
Two eyewitness statements, provided on Wikipedia recounted the following:
The atmosphere was explosive. Many in the crowd seemed to be intoxicated. When people started falling off the stairs and pulling others with them, it became just chaotic. They just couldn’t be stopped. It was a living hell.
I will never forget the sight. There were all these twisted-up bodies of those who had been crushed. They were lying at the tunnel exit. Their faces had all turned blue.