I read up on this stuff too. Definitely a mass murderer. I don’t know how that can be contradicted. He murdered. A mass of people. Ipso facto …
Spree killer? I don’t think so. Usually a spree killer doesn’t target specific individuals for specific reasons. Even Klebold and Harris targeted types of people (they were after “jocks”, not a specific jock) for perceived sins (although rooted in a rationalization (bullying)).
That is to say, spree killers usually get fed up with something and decide to kill someone. This guy was pissed off about a specific thing and went after specific people to punish them.