Any shot fired by anybody in less than a 100% straight up and down line is going to be deadly, somewhere.
They did a Mythbuster's episode where they discovered that if you did fire a gun straight up, it's ammunition was not dangerous when it returned to earth. However, if it had any of it's ballistic arc intact, it retained it's lethality and since most humans can't fire straight up, somebody might be dead. (I know their science is sometimes a bit flaky but not this time.)
While a running crowd can be dangerous, a couple of semi-auto rifles with plenty of ammo, grenades, etc., is going to be a lot more lethal. I pick the less lethal system.