Matt,
Would you agree that these "several in the crowd" who were 'armed" would have most likely only carried pistols? Sir, according to what I read, the shooter was over 1000 feet (304.8 meters) from the crowd. The relatively low velocity of pistol rounds, coupled with short barrels, makes one practically ineffective at that distance. You would most likely hit an innocent person than the perpetrator so discharging a handgun would be reckless at best.. Only a rifle or something like a shotgun slug would have worked at that distance and nobody walks around with one of those stuck down in his waistband.