In a gesture of solidarity following the gruesome killing of a French priest, Muslims on Sunday attended Catholic Mass in churches and cathedrals across France and beyond. Reporters say that between 100 and 200 Muslims gathered at the towering Gothic cathedral in Rouen, only a few miles from Saint-Etienne-du-Rouvray, where the 85-year-old Rev. Jacques Hamel was killed by two teenage attackers on Tuesday.