Just to qualify what some people are saying.
Although there is nothing to suggest, and indeed a clear statement that he did, die of natural causes, at home with his family around him, and that in the past year his health deteriorated very rapidly.
There can exist a situation where a person can die and not require assisted suicide, they can simply commit suicide. The assisted bit applies to those unable to administer drugs to kill themselves, there is nothing to stop someone in stages of dimentia just killing themselves at a time they find convieient and appropriate.
Not remotely suggesting that is what happened here. Just wondering why everyone immediately started asking regarding assisted suicide which in the case of dimentia is most unlikely to apply, as perversely in the latter stages a person cannot conscent to an assisted suicide, and conscent can't be carried forward over a number of years of decline.
Any assist in end stage would be termed murder, even in switzerland at dignitas.
I loved his character of death, my favourite.