I feel very sorry for the families of these to men.
But this is a good reason for having a contingency plan in the case of such an event.
I live in Australia so have no idea of the area they were in ,but they should have agreed on what they would do in the case of an emergency especially at their ages and level of experience. You can accept someone of this age having a heart attack and possible death but for your buddy to share the same fate, through lack of planning is not good.
My 2 mates and I do quite a bit of deer hunting during the winter in cold mountainous country. We have agreed if something were to happen to one of us we would not attempt to walk out late in the day. We believe it would be better to stay together try the radio etc and leave at day light, you will have a lot going through your head to start with and its best to have everything in your favour if there is an emergency.