Over at Scott Aaronson's blog his father has mentioned that, according to the coroner, he may have had undiagnosed type-I diabetes [1]. His father also mentions that Michael supported the charity givedirectly.org if anyone prefers to offer condolences that way.
It's a sad event for the theoretical CS community. I didn't know Michael, but looking at some of the other memorials some prominent researchers have written ([2], [3]), he appears to have been an extremely promising researcher and collaborator.