I believe that is not quite right. The first spree was on December 30, 1974 at the Olean High School in Olean, NY by 17 y/o Anthony Barbaro. However, it was not while school was in session, so you could debate about that.
But this kind of continuing issue was predicted by Erica Carle, on May 2, 1974 (as noted in her 2003 article SHOOTING RAMPAGES: WHY DO CHILDREN KILL?). That 1974 article was geminal, I believe, in projecting the outcomes of the sea change in high school indoctrination in the human arts. Her prescience is worthy of reviewing.
Regarding Prozac, it was preceded by other such benzodiazepines, starting with Librium (chlordiazepoxide) in 1953, Valium (diazepam) in 1963, and others subsequently. (Is it possible that Anthony Barbaro was being treated with one of these earlier varieties?)
FYI
Correction:
Librium (chlordiazepoxide) in 1960
Sorry --