The only one earlier than Columbine which comes to mind, is the San Ysidro massacre of 1984, near San Diego, where a nut shot about 20 people.in a McDonald’s.
It does seem that there are more mass shootings. But there s also more saturation coverage on news channels of such events too.
San Diego 1984 Macdonalds shooting involved 40 victims...
1966 UT tower shooting had 15 fatal and 30 wounding hits...stop adding to the wizardry of fake news hyperbole!
Kip Kinkel, Thurston, OR, 21 May, 1998.. A year before Columbine.