There?s a fictional short story or poem story that takes place during
the US Civil War. A soldier is sitting on his horse on one side of a
canyon or mountain. Another soldier on the other side of the canyon
shoots his horse out from beneath him and the man falls to his death.
When the soldier?s commanding officer ask him why he shot the horse
rather than the man, he replies that he couldn?t shoot the man because
it was his father.

I need to locate this story online.

I am confident that the story you're looking for is "A Horseman in the
Sky," by Ambrose Bierce.

You can read the entire story here:

Civil War Home
http://www.civilwarhome.com/Sky%20Horse.htm

Google search strategy:

Google Web Search: "bierce" + "horseman in the sky"
://www.google.com/search?hl=en&ie=UTF-8&q=bierce+%22horseman+in+the+sky

If this is not the correct story, or if the link doesn't work for you,
please request clarification, and I'll be glad to resume the quest.

Best wishes,
pinkfreud

Thanks