Thoughtful of you! :-) What a mess!
Even at that point blank range, I can't see 7.62 X 39 hardball doing that level of damage. I suspect dum-dums or some sort of expanding slug...
What “level of damage” is needed in a stadium to start a panic stampede? 150 grains moving at even 800FPS is about like getting shot with a mild .38 Special, but with more damage since the long .30 caliber rifle slug will be keyholing and tumbling through the air. A stadium upper deck is a very big target, even at past 1,000 yards.