From Facebook:
Late this afternoon David [Hartwell] had a massive brain bleed from which he is not expected to recover.
Hartwell was John C. Wright’s editor at Tor Books; he was also friendlier to the Puppies than any of the SF-SJWs are likely to believe. I had the privilege of speaking with him when he called me last year after the Rabid Puppies overturned the SF applecart; he was the previously unnamed individual who explained the unusual structure of Tor Books to me, using the analogy of a medieval realm with separate and independent duchies. He wanted to avoid cultural war in science fiction even though he clearly understood that it appeared to be unavoidable; it was out of respect for him that I initially tried to make a distinction between Tor Books and the Making Light SJWs before Irene Gallo and Tom Doherty rendered that moot.
Despite his leftward leanings, David Hartwell struck me as being one of the last remaining sane individuals in the editorial offices there, and he was perhaps the only one capable of reigning in the lunatic impulses of Patrick Nielsen Hayden and the Torstapo. By his own account, he even managed to talk the notorious award-whore into standing down and letting long-time bridesmaid Lou Anders of Pyr finally win PNH’s Best Tor Editor Award (also known as Best Editor (Long Form) Hugo) in 2011.
I expect he will be missed by many, and that things in the science fiction world are going to get even more, shall we say, interesting, in his absence.
UPDATE: David Hartwell has died. Requiescat in pace.