Thousands gathered in St. Peter's Square as Pope Francis' casket was brought for three days of viewing. The pontiff, who died Monday at age 88, will be celebrated this Saturday in an elaborate funeral mass.

Pope Francis, 88, died April 21, the Vatican announced. No cause of death was included in the statement. In February, after a bout with bronchitis, he had been hospitalized in Rome with what Vatican officials called a “complex clinical picture” that included a diagnosis of double pneumonia.