What happened in "The Signal-Man" after the appearance of the ghost?

In "The Signal-Man," the ghost appears on three separate occasions, two of which are followed by terrible accidents on the line. After this, the story begins: the narrator meets the signalman and follows him down to his signal box. After some confusion over his identity, the signalman confesses to the narrator that he has lately experienced some strange events and the pair agree to meet the next night so that the signalman might relate his tale.

The next night is, therefore, filled with anticipation. The pair sit around the fire and the signalman tells the narrator about the ghostly appearances. Initially, the narrator is very sceptical and dwells on practical explanations of these supernatural occurrences, like a disorder of the eye:

I showed him how that this figure must be a deception of his sense of sight; and how that figures, originating in disease of the delicate nerves that minister to the functions of the eye, were known to have often troubled patients.

But the signalman's distress is so evident that the narrator begins to realise that he is telling the truth:

His pain of mind was most pitiable to see. It was the mental torture of a conscientious man, oppressed beyond endurance by an unintelligible responsibility involving life.

This meeting closes with the narrator's resolution to prove the signalman's state of mind by involving a highly-respected doctor. The pair then bid each other goodnight, on the agreement that they will meet again the next day.

When the narrator makes his way to the signal box, the next evening, he is surprised to find a group of men assembled down below. He is gripped by the "irresistible sense" that something is wrong and begins to question the men to find out what has happened. In a tragic twist of events, the narrator is horrified to learn that the signalman has been killed and this prompts the realisation that the ghostly apparitions were, in fact, a premonition of the signalman's own demise. He also learns that the only witness to the event had uttered the very same words that the narrator had once said to the signalman:

"Below there! Look out! Look out! For God’s sake, clear the way!”