For simplicity, let’s assume that you value all human equally. Then the question if not if he could have saved a life. The question is if (under similar circumstances) the probability of dying was less than the probability of saving the other person. I think it’s not reasonable to attempt a rescue with a 90% dying chance, knowing that there is only a 10% chance of success. On the other hand I think it’s reasonable to attempt a rescue with a 10% dying chance, knowing that there is a 90% chance of success. It’s very difficult to estimate the chances in this case, because we don’t know all the circumstances, the available information and the point of view. And it’s impossible to be sure how I would have reacted in the very short time that was available.
And if you want a more complex model and don’t mind using made up numbers, I’d prefer to weight myself and my family members with 2 points, and give my daughter at least 5 points.
Condolences to both families.