"One of the Negro Confederates was only wounded, but the other was killed one afternoon after leaving the security of a hollow tree (probably to relieve himself). Two Confederates tried to get to his body but were driven away by the Union gunfire" Alfred Bellard,
Gone for a Soldier, p. 56So far all you've provided is an account of two black men getting shot by Union forces while trying to relieve themselves.
What company were they in?
What was their rank?
What battle was being fought?