today, ash wednesday, benedict explained his decision to retire saying, "i am no longer capable of carrying out peter's ministry with the strength needed." allen pizzey is in vatican city. >> reporter: flash photography is frowned upon in saint peter's basilica, but it was a sin worth committing today as the faithful crowded in to get a glimpse of the pope at his last public mass. benedict's frailty, which played a part in his decision to resign, was evident. but so too was the faith and sense of duty which made him take a job he said he never wanted. he said the mass was a good opportunity to thank everyone and ask for a special remembrance in prayer. he used his sermon to criticize recent infighting among priests at the vatican, saying the church's image had been hurt. the mood was bittersweet, tears wiped away discreetly. [ applause ]