I still think it's very different than the incidents listed in that chart, for instance. I'm not sure where the line is drawn, but I think for something to be considered a "mass shooting" there has to be more than 2 victims (OK, well I guess this has 3 including the woman being interviewed who was not mortally wounded)
I also think it's different because he picked specific targets and knew his victims, they were his co-workers. They were not just random people who happened to be in a certain place that he was targeting.
just heard something on the radio (missed the full story) that this killer, Vester Flanagan (?), sent a "manifesto" to ABC News that cites the recent Charleston, SC shooting as a tipping point, and also mentions he admires the Columbine and Va Tech shooters
https://abcnews.go.com/beta/US/shooting-alleged-gunman-details-grievances-suicide-notes/story?id=33336339