What makes a Military leader great? The fact that they can put aside personal feelings to do the greater good. I was a Fire Marshal on a Fast Combat Oiler (supply and weapons ship). We had an emergency diesel generator spring a leak during a blackout. I was in charge of the fire fighting parties. I had them close hatches and scuttles, thus locking ourselves in. We put down foam and waited as the electricians secured power and BTs shut down the diesel. A few days later, an officer complained to the captain about what I did. The captain chastised the officer, because I was willing to sacrifice 50 people to save 1,000.
In the scenario you postulated, it is better to save the younger, stronger people, because they will be useful by God to rebuild. Hard choices, yet many people would not see the dire need to do the right thing.