My father disappeared slowly and quietly, and it was a gradual process.
I never felt very close to him, but I always wished that we had been closer.
Now he is a shell of who he was, barely present anymore. Cancer, pain, and painkillers have taken him away from this world for the most part. There is still a shell of a man left, but he's mostly gone.
Needless to say, I see this as one of the downsides of modern medicine. It would have been much better for him to have a quicker, easier death.