A very sad series of events. I wonder if current knowledge might have saved him? Or, considering just how fast and how silent a killer this condition can be, maybe it was just inevitable.
Complicating all those incidents, IIRC: supposedly Hunter was very reliant on alcohol to get through a typical day, and some of those incidents might not have happened if he'd been sober more often. (Also from Inside Star Trek: The Real Story
by Herbert Solow and Robert Justman, IIRC.)