One of the issues in the gun debates is that the number of victims in mass shootings is tiny compared to the overall gun death rates.
Of course that is not true. Aside from the deceased we have the wounded, the co-workers who were shot at or hid, the families of all these people, the friends, etc.
Plus the utter randomness of targets as well as the fact that the slaughters taking place in normally safe areas. Shopping centers, schools, churches, concerts, offices, theaters are no longer safe in the minds of many who were close to a shooting by kin, friendship or as witnesses.
Effectively the damage is much worse than if a person got robbed and shot in a tough part of town. Or as a gang member. Or trying to score some dope. Or in a bar fight. Or even a domestic situation.
450 people is astounding, but not surprising. If this were the first such shooting in years, maybe a raised eyebrow would be warranted. But now that mass shootings are common place, when they hit close to home it traumatizes a lot more, in my opinion. And this only counts those workers in the building. Not outside relations.
This is something the gun lobby should heed before leaning too heavily on the body counts to minimize the impact of random shootings.