The tone of this story is dark and and gloomy, but also contains some happy points within it. Parts of the story such as Doodle's death and the storm show the dark and gloomy scenes that this story contains.
The word choice in this story is matching with the tone as dark and gloomy. Many words such as kill, crying, and smothering show a dark tone and show that something bad is happening.
"The rain was coming, roaring through the pines, and then, like a bursting Roman candle, a gum tree ahead of us was shattered by a bolt of lightning." The scene of the story is happy, but at many points of the story it's stormy and dark.
The style of this story is fiction, but also has contents of horror as the narrator talks about smothering his brother with a pillow.
The theme of the story is to realize what you have before it is gone. The narrator always thought that his brother was more of a burden, but during the end of the story, and after Doodle's death, he realized that he really loved his brother.