The Knife by Richard Adams (2011) in Stories, edited by Neil Gaiman and Al Sarrantonio, Harper Perennial

Like Poe’s “Tell-Tale Heart”, this story is told from the point of view of a character who has done something criminal.  It traces the discovery of a murder weapon, and the bullying that pushes the narrator to the reprehensible act.  And the confession to a dear uncle who chooses to keep the secret.