Pope Francis addressed the scourge of child sex abuse in the Catholic Church in unscripted remarks Sunday. He said "great harm" has been caused by the clergy sex abuse scandal over the last decade. Pope Francis met with survivors of abuse Sunday and vowed to hold clergy responsible for these crimes accountable. "Those who have survived have become true heralds of mercy," Pope Francis said. "Humbly we owe each of them our gratitude for their courage." The pontiff wrapped up his historic six-day visit to the U.S. with an open-air mass before hundreds of thousands in Philadelphia. "May God bless you all — God bless America," Francis said before he boarded a flight back to Rome.