http://blackfridaydeathcount.com/ Crowd control is difficult, whatever the venue.
http://matadornetwork.com/nights/10-deadliest-concert-disasters-of-the-last-50-years/
https://en.wikipedia.org/wiki/List_of_violent_spectator_incidents_in_sports
The authorities who run the venue try to anticipate problems, as one would with any large event and it was a failure in crowd control. They are investigating and will attempt measure to prevent it happening in the future.