Pale Rider

In the countryside outside the fictional town of Lahood, California, sometime around 1880, thugs working for big-time miner Coy LaHood ride in and destroy the camp of a group of struggling miners and their families who have settled in nearby Carbon Canyon and are panning for gold there. In leaving, they also shoot the little dog of fourteen-year-old Megan Wheeler. As Megan buries her dog in the woods and prays for a miracle, a stranger passes by heading to the town on horseback.
Megan's mother, Sarah, is being courted by Hull Barret, the leader of the miners. Hull heads to town to pick up supplies, where some of the same thugs begin to beat him up and he is rescued by the stranger, who takes the three men on single-handedly. Hull invites him to dinner at his house, and while the stranger is washing, Hull notices what looks like six bullet wounds to his back. Shortly after, he appears wearing a clerical collar and thereafter is called "Preacher".
Coy LaHood's son Josh attempts to scare Preacher with a show of strength from his giant work hand, Club, who with one hammer blow smashes a large rock that Preacher and Hull had been laboring over. When Club attempts to attack Preacher, he hits him in the face with his hammer and delivers a blow to Club's groin. Coy LaHood has been away in Sacramento and is furious to learn about Preacherâs arrival through his son, since this will stiffen the resistance of the tin-panners. Having failed to bribe him to settle in the town instead, LaHood offers to buy the miners out, initially for $100, then $125 and then the Preacher goads him into raising his offer to $1,000 per claim, but only if they leave within 24 hours; otherwise LaHood threatens to hire a corrupt Marshal named Stockburn to clear them out.
The miners initially want to accept the offer but, when Hull reminds them why they came and what they have sacrificed, they decide to stay and fight. The next morning, however, the Preacher disappears. Megan, who has grown fond of the Preacher, goes looking for him, but Josh confronts and attempts to rape her, while his cohorts look on and encourage him, except for Club, who sees what is happening and moves forward to help Megan before Josh can do anything serious. At this moment the Preacher arrives on horseback armed with a Remington Model 1858 revolver he has recovered from a Wells Fargo office and, after shooting Josh in the hand when he goes for his gun, takes Megan back to her mother in the mining camp.
Stockburn and his six deputies arrive at the town and LaHood describes the Preacher to Stockburn, who appears startled and says that he sounds like someone that he once knew, but that couldn't be, since that man is dead. Stockburn and his men gun down Spider Conway, one of the miners, who was drunkenly shouting insults to LaHood from the street. Stockburn tells Spider's sons to tell the Preacher to meet him in town the next morning.
The Preacher and Hull go to LaHood's strip mining site and blow it up with dynamite. To stop Hull from following him, the Preacher then scares off Hull's horse and rides into town alone. In the gun fight that follows he kills all but two of LaHood's men and then, one by one, all six of Stockburnâs deputies as they search for him throughout the town. Finally, he shoots it out with Stockburn, who recognizes him in disbelief before the Preacher kills him. Coy LaHood, watching from his office, aims a rifle at the Preacher, only to be shot and killed by Hull coming in through a back door.
The Preacher rides his horse out of a barn and by way of thanks remarks to Hull "Long walk" before riding off into the snow-covered mountains. Megan then drives into town and shouts her love to the Preacher and thanks after him. The words echo along the ravine that he is traversing.

Question: In the movie, why does Stockburn say that the Preacher could not be the man he once knew?
Answer: that man is dead; that man is dead