One of the things we quickly learn about the engineer is that he is dependable, loyal, his life is made up of the routine of the train and the constant back and forth on the same route. He traveled the same route day after day, year after year, for two decades and found great and simple pleasure in the fact that he would blow the whistle in the same place, the same woman would come and wave, and her daughter joined her.
From a distance, this process gave him great hope that there was something more in humanity than the horrors he had seen on the train, the cruel tragedy visited upon those who found themselves in the way of this methodical and powerful beast. He placed in those two women his hope and his faith that there was something more.
We learn at last that his hopes are dashed when he meets them, when they greet him with suspicion and fear instead of acceptance and joy. The despair that filled him upon seeing those tragedies from the locomotive now has nothing to hold it back.