Echoes from the Square by Elizabeth Wellburn, illustrated by Deryk Houston

This picture book was inspired by the story of Vedran Smailovic. During the Bosnian war, he witnessed 22 people killed in the street near where he lived and played his cello in a square in Sarajevo for 22 days as a memorial to the victims.

Fromchapters.ca:
Echoes from the Square tells the moving story of a boy’s terror and grief in wartime. With his friends killed and maimed, the boy learns to hope again when he meets a cellist playing in the street.