Pope Francis, who served as the head of the Roman Catholic Church for more than 12 years and was the author of more than 20 books, died Monday at 88, the Washington Post reports.

Francis was born Jorge Mario Bergoglio in Buenos Aires, Argentina, and worked as a bouncer, janitor, and laboratory technician before joining the Society of Jesus, or the Jesuit Order, in 1958. He became a priest in 1969 and was named the archbishop of Buenos Aires in 1998. He was appointed as a cardinal three years after that.

Francis was elected to the papacy in 2013 after his predecessor, Pope Benedict XVI, resigned. As pope, he was a vocal supporter of peace and justice issues, heavily criticizing capitalist excess and apathy toward climate change, and he was known for his outreach to LGBTQ+ people.

Francis’ early books include Meditations for the Religious, Putting the Motherland on One’s Shoulders, and The Nation To Be Built. He published his first book as pope, The Church of Mercy, in 2014. Several others followed, including Happiness in This Life, translated by Oonagh Stransky; A Future of Faith, co-written with Dominique Wolton and translated by Shaun Whiteside; I Am Asking in the Name of God, translated by Stephen R. Di Trolio.

He published two memoirs during his papacy: Life, co-written by Fabio Marchese Ragona and translated by Aubrey Botsford; and Hope, co-written by Carlo Musso and translated by Richard Dixon. The latter was published in January.

Francis’ admirers paid tribute to him on social media. On the platform X, Ukrainian President Volodymyr Zelenskyy wrote, “Millions of people around the world are mourning the tragic news of Pope Francis’s passing. His life was devoted to God, to people, and to the Church. He knew how to give hope, ease suffering through prayer, and foster unity. He prayed for peace in Ukraine and for Ukrainians. We grieve together with Catholics and all Christians who looked to Pope Francis for spiritual support. Eternal memory!”

And former U.S. President Barack Obama posted, “Pope Francis was the rare leader who made us want to be better people. In his humility and his gestures at once simple and profound—embracing the sick, ministering to the homeless, washing the feet of young prisoners—he shook us out of our complacency and reminded us that we are all bound by moral obligations to God and one another.”

Michael Schaub is a contributing writer.