Everything in this thread is pure speculation. What could have been done, what should have been done, what you or I could do, or would do, will always be speculation. We do not know.
I have on occasion saved people from greater or lesser peril at some risk to myself. On a few occasions I have chosen courses of action or inaction that were short of "heroic". I can't tell you the exact reasons for either, it just happens. The outcome of any of it, as anyone who has been in these kinds of situation will tell you, is pure fate. There is no conscious decision, you just do or do not, and you don't know which it was, or what you could or should have done, but didn't, until it is over.
What we do know is that a man pushed another man off the platform in front of an oncoming train. We know who was killed and by whom. Everything else is lost to the fog of war, even, most likely, to those present. Perhaps for someone who was present there is some miserable hindsight available. It may or may not be 20/20, and i feel for that person. But there is no hindsight whatsoever for armchair speculators. We like to talk big, but we weren't there. We don't know. I find it fascinating that so many think they do.