The Vatican described his condition as critical for the first time on Saturday, reporting that the 88-year-old Francis needed supplemental oxygen and blood transfusions after a "prolonged asthma-like respiratory crisis.

The death of a sitting pope initiates a profound period of mourning and transition within the Roman Catholic Church, marked by a meticulously structured process to elect a new pontiff

Many who know him said that Francis, driven by a sense of mission and a discipline born of his early training, essentially worked himself into the hospital.