Following up on the Saget thing, this article provides the latest theory as to what might have happened - he hit his head on the marble bathroom floor, regained consciousness, wasn't aware enough to understand how bad his injuries were or wasn't able to call for help, made it to the bed, and eventually died.
What Really Happened to Bob Saget? New Details on His Final Hours
What this vaguely reminds me of, although not nearly as severe, is the Porco murder case from NY about 15-20 years ago. Chris Porco attempted to murder his parents with an axe while they slept. His mother, deformed, survived (and still believes her son is innocent). His father did not - however, he did not immediately die. About the only part of his brain that survived was the part that controlled basic functions. So when his alarm went off, dude was essentially dead but used the bathroom, shaved, went downstairs, loaded the dishwasher and did some other chores, went outside to get the paper, got locked outside but was able to get the spare key from under a mat, let himself in, and finally collapsed at the foot of the stairs from blood loss and died there.
Definitely seems like something similar happened with Saget. He was conscious enough to get up and move, but unable to recognize his injuries or do anything about them, got to the bed, probably lost consciousness again, and died.