Joseph E. Duncan III, the notorious serial killer responsible for the brutal slayings of a Coeur d’Alene family, died while awaiting execution, prosecutors in California said in a statement Sunday. Duncan died Sunday at a hospital near the federal prison in Terre Haute, Indiana, according to the statement from the Office of the District Attorney for Riverside County. He was 58. One of Duncan’s victims, 10-year-old Anthony Martinez, was a resident of the county. “The sun is brighter today, and my soul is lighter,” Anthony’s mother, Diana, said in the statement. “The world is a more beautiful place without the evil that is Joseph Duncan. God chose to make his end a long suffering and I believe that is fitting. The horror of his thoughts consumed him.” In 2005, Duncan killed Brenda Groene, her boyfriend Marke McKenzie and her 13-year-old son, Slade, in their home near Coeur d’Alene. Duncan also kidnapped 2 of Groene’s other children, Shasta, then 8, and Dylan, 9. After abducting the 2 chi