In a strange echo of what happened with George Clayton Johnson, there have been announcements - followed by rapid retractions - of the death of Hugo Award-winning editor and critic David G. Hartwell. He evidently suffered a massive stroke.
I once sat on a conference panel with David, although my interaction with him was minimal. But I am very familiar with his work. The "Timescape" imprint he started at Pocket Books in the 1980s gave me plenty of quality reading back in the day, and that accounts for only a tiny proportion of his career's work. You can read about this influential SF figure here: https://en.wikipedia.org/wiki/David_G._Hartwell
This photo shows the panel at the 2008 Eaton Conference at University of California Riverside where I met David. Left to right: Paul Alkon, David G. Hartwell, Eric Palfreyman and me. The theme of the panel was the Mars and Ray Bradbury, and the whole conference was entitled "Chronicling Mars".