Why did this story make a "shocking impression" on the narrator?

The narrator is close with his priest and is worried about his safety.
The narrator can't stop thinking about Hell specifically.
The narrator is preoccupied with the idea of Confession.
The narrator wants to help the mysterious fellow.

The story made a "shocking impression" on the narrator because it made him realize the consequences of sin and the reality of Hell. He was also worried about the safety of his priest, and the idea of Confession and helping the mysterious fellow made him think about his own spiritual state.