That's how my grandfather went, at the end of years of steadily worsening Alzheimer's. We kept suggesting to my parents that they suggest to the staff that he was "in pain", but they wouldn't. It took him over 2 weeks to die. It was a terrible thing to watch, and seemed completely pointless- you've already decided that he's going to die, why prolong it? Somehow doing something to "help him along" is killing him, but withholding food and water is not. :(