I'm shocked, saddened, but not very surprised. Tom had been depressed for several years and was especially hit by the death of his longtime partner Charles Naylor. He also was very worried about being evicted from the rent controlled apartment he lived in for decades.
I last visited with him about a month ago, when I ran into him shopping at the Greenmarket across the street from where he lived (he rarely went out because he had trouble walking). He invited me up for cheese and bread which we bought together at the market and I visited for an hour or two. He seemed more optimistic about his work than he'd been for at least a year as he had three books/novellas coming out over the next year.
Tom wrote wonderful stories (I only read one or two of his novels but kept meaning to read more) and if you haven't ever read the collections Getting into Death or Fundamental Disch you need to find and read them.
Tom, as much as you were a bitter, sometimes mean curmudgeon--I'll miss you.
John Clute on Tom Disch
And possibly the best obituary by Elizabeth Hand on