I  only saw a small part of this movie and it was about 15+ years ago.

The only part I saw (and what I remember of it) goes like this:

There was a young boy who was sleepwalking or something in the middle of the night while walking on train tracks. From all the way in the house the father starts hearing a Distant  train whistle and starts to panic and run toward the train tracks which was across a field or something. He gets to the tracks just in time to jump and push the son off of the tracks but he gets his whole lower half of his body run over by the train.

I know its not very descriptive but that was all I saw. It’s bothered me for years not knowing what it is because it left a horrifying fear when I hear distant train whistles.