We need to find out more information about this tragedy, but I find the second explanation much more plausible, and I would guess that what may have happened was that a surge of people leaving the stadium met another crowd in the city centre going in a different direction creating a fatal crush. I would also predict that the majority of fatalities would be due to asphyxiation rather than being trampled by others.
Cocking C. (2013) Crowd flight during collective disorder- a momentary lapse of reason? Journal of Investigative Psychology and Offender Profiling. http://onlinelibrary.wiley.com/doi/10.1002/jip.1389/abstract
Johnson, N. R. (1987b). Panic at ‘The who concert stampede’: An empirical assessment. Social Problems, 34, 362–373.