Mysterious Man In A Train

There was a man,karan who was once travelling by a train. While travelling he met an old man. After some time they start talking to each other and the old man told a story which was real. He told, "Once there was a train driver who was driving the train very fast. Because of this he could not stop the train at a bridge and this led to the death of young boys. After this accident he resigned  from his job and felt very regretful." After hearing this, Karan asked him, whether he knew the name of the driver. Now  the old man smiled and told that he was the driver of that train and after hearing this karan was shocked. He asked surprisingily that why did he do this. Now the old man did not answer his question and got off the train, to his respected station. After this, Karan always thinks of meeting that man once again in his life and continue his story.....