Pope Francis met with victims of child-molesting priests Sunday on the final day of his U.S. visit and promised to hold accountable those responsible for the scandal, delivering a powerful warning to American bishops accused of covering up for pedophiles instead of reporting them to police.
The pontiff disclosed the gesture of reconciliation at the start of a meeting with U.S. bishops gathered in Philadelphia for a big rally on Catholic families.
Francis praised the victims as "true heralds of mercy" who deserve the church's gratitude and said sex abuse in the church can no longer be kept a secret. He promised to "zealously" protect young people and see that "all those responsible are held accountable."
Francis has agreed to create a new Vatican tribunal to prosecute bishops who failed to protect their flock by covering up for pedophile priests.
Victims' advisory groups had complained earlier in the week that Francis had neglected to address their plight when he congratulated bishops for their "courageous" and generous response to the scandal.
On Sunday, he directed his attention to the victims in a city hit hard by the scandal. The Archdiocese of Philadelphia has been the subject of repeated grand jury investigations, and a monsignor was convicted of endangering children by not removing pedophile priests.
Later Sunday, Francis was scheduled to visit a prison and celebrate a final Mass on U.S. soil on Philadelphia's grandest boulevard, the Benjamin Franklin Parkway.
Organizers said they expected 1 million people to turn out. But there were fears that the extraordinary security -- including airport-style bag searches, crowd-control cattle chutes and blocked-off streets -- would scare away many.
Roman Catholics from across the country and around the world began making the trek to the Mass hours ahead, crossing bridges on foot and packing subway cars.
At Curran-Fromhold Correctional Facility, Francis planned to visit with 100 inmates, including suspected killers, rapists and mobsters. He was expected to offer them words of hope, forgiveness and redemption.
"His mission is the marginalized, the forgotten," prison spokeswoman Shawn Hawes said. "From our understanding, he wants those who are in custody to know that they are not forgotten and they can be redeemed."
Prison ministry has been a hallmark of Francis' pontificate. He meets often with inmates and has washed prisoners' feet during pre-Easter rituals. He opposes the death penalty in all circumstances and has called for the abolition of life imprisonment and solitary confinement.
On Saturday night, Francis was cheered by tens of thousands at a music-and-prayer festival on the Parkway, waving to the crowd in his open-air popemobile. Performers included Aretha Franklin and Andrea Bocelli.
He called families a "factory of hope," even with their imperfections.
"Defend the family, because that's where our future will play out," he said.
Thomas Coorey, a dentist and father of four visiting Philadelphia from Sydney, called Francis "the most inspirational and amazing pope that could breathe life into this church of mine. And I'm so grateful to have a leader like him who's so humble and such a true servant of God."
It's been a common sentiment throughout the pope's visit to Washington, D.C., New York and Philadelphia.
"It's the wave. It's the smile," said Tom Hambrose, 52, of Haddon Heights, New Jersey, attending the Festival of Families on Saturday night. "It's what he's articulating, that the church needs to step forward and needs to change its thinking about things."
Associated Press writers Michael R. Sisak, Maryclaire Dale and Kathy Matheson contributed to this report.