In the first stanza, the tone starts off as calm and contended. To obtain that feeling of serenity, he uses words that paint a placid scene. He says "it is snowing softly," which brings to mind a quiet snowfall, instead of a blustery snowstorm. It is the "twilight of early evening" which brings to mind the settling, peaceful dusk of the day that is not bright with sunlight or harshly dark, but filled with softened colors. He has "neatly folded clothes" to convey a sense of order, and that all is right in the world, with no surprises. There is a "glow in the hollow of his cheek" which brings to mind health, warmth, and happiness.
In the first of stanza two, the tone becomes completely objective, meaning factual and dry. The author uses straight-up words without ornamentation to describe the poverty of the man. He is "very skinny, dressed as one of the poor." He leans to put his laundry in the car. Then in the second half and stanza three, the tone changes to rushed and dramatic. The author uses words such as "flurry of footsteps", "cries of pedestrians," "shooting a pistol, firing it," and "grabbing at his chest". All of these words are intense, and make the feeling more anxious. He uses abrupt punctuation such as dashes ("a boy-that's all he was-") to give the mood an abrupt and surprising feel, just as the gunshot is surprising.
In the fourth stanza, the tone changes again, and becomes more emotional, ponderous, and personal as the narrator comes in with commentary. To make it ponderous, he mentions "Descartes' grand courage"; Descartes was a philosopher who proclaimed, "I think, therefore I am," so mentioning him automatically sets a mood of pondering. He uses the first person, "I feel so distinct" to make the tone personal and emotional.
In the last stanza, it is distant, and very solemn, almost like a eulogy at a funeral. To bring about that tone, Hongo uses platitudes such as "Let the night sky cover him," invoking grand gestures and speeches given at formal events, which makes it all very grave.
I hope that helped a bit; I included links to further discussions of theme and tone. Good luck!