No they're not. The first reconized school shooting was in 1764, with the Enoch Brown school massacre. There have been school shootings ever since. (Unless you want to argue that the 1700s wasn't that long ago, which it also wasn't, but I don't think that's where you're coming from.)
Well, we're approaching the 25th anniversary of Columbine. But 35 years ago, my neighborhood was equipped with quite a lot of Uzis and Mac-11s, and we had quite a lot of mass shootings. Only they were called "drive-bys" and nobody circled the wagons to preserve the historical tradition of access to such equipment.
At what point did ordinary people get easy access to weapons that have high capacity and rapid fire? That's when we see a rise in mass shootings. Today, ordinary people are getting access to tools which can quickly and easily make better fakes than experts with photoshop could do even 5 years ago.
https://en.wikipedia.org/wiki/List_of_school_shootings_in_th...