The nazis did not spare anyone; they even forced 90-year-olds into the trains.
If this guard were to receive the same measure, he should be deported somewhere.
But in *this* case the point is that no country will take him.He's a "hot potato".We can't just drop him out of an airplane...although more than a few would probably like that.
If this 94-year old is said to have committed crimes requiring the death penalty, deport him for trial. And if convicted, execute him.
If his alleged crimes do not merit the death penalty, drop the prosecution.