The park is waaayy over capacity today. Security is having a very hard time with the edges of the crowd, and there's lots of back-and-forth pushing. Folks are even climbing on top of the giant electric generators.
There are proper venues for this sort of event, and they're Hart Plaza and Chene Park, not Cass Park.
To cram 40,000 people into a 160,000-square-foot park and not predict that people will fall out from heat stroke in a little 2' X 2' patch of grass is cruel. They needed a much larger venue.