This is standard behavior for anything that happens around here like Easter egg hunts or Christmas/Start of School give-aways. The parents stampede, people grab everything in sight and take off. Punches are thrown. So far, nobody has been shot but it'll happen, you bet.
About 30 years ago or so, they had a "marshmallow drop" at the local fairgrounds......a zillion marshmallows were dropped from a helicopter over the crowd. The cops had to wade in and break up the fights. Fighting for what, you might ask......a marshmallow that's been stomped all over? Yuk.
After this, I imagine that most organizations are going to by-pass this kind of activity in the future. I don't think there's anyway to control a crowd of that size.