It's so sad but not unexpected. In a sense he died 2 years ago when the dementia was bad and he ceased to be able to communicate properly.
We're orphans now. He was 79 and our mother died at 75 only 3 years ago. That doesn't give us children a good life expectancy. The age your parents die is the best indicator of how long you will live.
He worked full time as a psychiatrist until he was 77.