With all those mental fuckers out there, I wouldn't be surprised someone drugged others intentionnally.
However, ''crowd turbulence'' is very real. Anyone who've been in the front of a crowd thats trying to go forward would have noticed. Even if it's a small crowd, you feel crazy pressure, even if people in the crowd doesn't seem to be pushing hard individually. With a huge crowd and if you are not very muscular to resist pressure, your rib cage breaks, organs punctured and you die. At the Love Parade festival in 2010, 21 people died that way. Crazy stuff.