What if?: What would've Kenny done if duck did kill everyone on the train?

This has played on my mind a bit? but let's say there's a universe in which Lee fails to communicate his willingness to get kenny to stop the train and Kenny kicks him out. Obviously he goes back and finds Duck has soloed his own mother, a little girl, a teen and a homeless dude very capable of defending himself. And then kills him falling of the train.

But if this continued what does Kenny genuinely do when he stops for the tanker, goes back to see his wife and child and find everyone dead or reanimated all because he was too stubborn to see the reality duck was dead. Not only that he wouldn't even know what happened to duck since he fell off the train with Lee.