So, the shooter was a non-insane, Bernie-supporting, Trump-Hating Progressive. My first suspicion was a politically incoherent lunatic like the Portland stabber or the guy who shot Giffords, but this guy fits #2 on my speculative list.
Enough back-patting ... IOW, the shooter was on the fringe of the Lib-Prog mainstream, basically like a DU-member who went out and did the violence DU-folk constantly cheer (Antifa, Kathy Griffin, Donaldus Caesar).