"In Mauthausen, Austria, we remember B. Marcello Callo, martyr, who, a young native of Rennes, comforted his fellow prisoners, exhausted by the gruelling labour of the work camps, with his great passion for Christ, and for this reason met his death in the extermination camp of Mauthausen. (19 March)"
January 1, 1970
https://en.wikiquote.org/wiki/Roman_Martyrology