I find it interesting that the politicians and pundits are all over the place in finding the correct term to describe the event. The clip below from Politico provides a vignette.
I think that it is symptomatic of the trauma so many Americans feel over the events of 9/11 that they do not want to use a term that conjures up those emotions. Clearly, this was not on the scale of a 9/11 but as Charles Krauthammer noted, seeing the smoke and people running is a psychological echo of that history.