The tone is apologetic because the narrator only helped Doodle because he was embarrassed of him. It was not out of the goodness from his heart.
Style
The word choice is very dark because of the death of Doodle. The death of Doodle enabled the author to write words like weep and fallen.
Theme
When the deafening peal of thunder had died, and in the moment before the rain arrived...
The style of the story is more of a narrative because it tells a story on how an older brother selfishly taught his disabled brother basic needs in life.
Doodle, swim!
The theme of the story is that you should not take things for granted. The narrator felt guilty after Doodles death because he only helped Doodle because he was embarrassed.