How would you describe the atmosphere established in the opening paragraphs of "The Pedestrian"?

The opening paragraphs of the story serve to establish the emotional atmosphere of the text as gloomy and foreboding. The word "silence" is used a couple of times, and the word "alone" is, as well. The air is "misty," and Leonard Mead is totally solitary. Actually, the reality is even bleaker than that: he is excluded from company of the people who live inside the homes that he passes. Walking by these homes is like "walking through a graveyard where only the faintest glimmers of firefly light appeared in flickers behind the windows. Sudden gray phantoms seemed to manifest upon inner room walls." Buildings are "tomb-like" and filled with "whisperings and murmurs." In short, it seems almost apocalyptic, as though Leonard is the only survivor: people inside their homes are described as phantoms, or ghosts, though the people themselves are not even visible. Everything seems dead—silent, gray, like a tomb—and this establishes a somber and foreboding emotional atmosphere of the story.

As a literary device, atmosphere describes how the feel of a place is inspired by details in a story such as objects, setting, or background. Atmosphere is slightly different from mood, though. While mood describes the internal feelings of the reader upon reading a particular piece of writing, atmosphere incorporates the feeling a particular location inspires.
In the story, the atmosphere established in the first paragraphs is one of abject loneliness and alienation. The setting is a quiet city on a misty evening, and the streets appear empty. Mr. Leonard Mead is the only human presence on the streets.
The "buckling concrete walk," intersections, and moonlit avenues are empty of human presence; the words "silence," "graveyard," "gray phantoms," "tomb-like," and "alone" further reinforce the feeling of isolation we get when we visualize this city in our minds. A feeling of decay and extinction is in the air. The author also tells us his story is set in 2053 A.D., seemingly a futuristic vision of a world gone wrong. His skillful use of atmosphere in the first paragraphs prepares us to expect dysfunction and uncertainty as we anticipate the resolution to the story.
https://literarydevices.net/atmosphere/