Pope Francis, who led the Roman Catholic Church for the past 12 years, has died. He died on Monday morning after suffering a stroke and cardiac arrest, according to the Vatican. Francis, who was 88, was known for being more progressive than most popes on social issues.

Pope Francis didn’t affirm same-sex marriage or lobby for ordaining women as priests. But he gently steered the Catholic Church in a more progressive direction while leading with compassion, openness and humility.

The pontiff’s death initiated a well-structured series of rituals designed to mourn the loss of the 1.3 billion-member church’s leader and to ensure stability with the selection of a new pope.