Think about how many school shootings there have been....... Now, think about how many shootings there have been at gun shows.

I think your point is a false equivalence. Mass shooters typically have a flavor of target I don't think gun shows provide. Most of them seem to be targeting the highest level of innocents and "normies" for a lack of a better word. Plus I think most mass shooters feel like gun shows are part of "their people", rightly or wrongly.

Like someone else mentioned I think they are after the biggest reaction and making the most amount of day to day life seem terrifying and terrorize average people in the street.