In 1904 he was ordained as a priest in a Roman Church of Santa Maria. Later in 1905, the new Bishop of Bergamo, Giacomo Maria Radini Tedeschi, appointed Angelo his secretary. Angelo went with Bishop Giacomo to all his pastoral visits. Angelo also helped him with many other tasks like managing the diocesan bulletin, going on pilgrimages, and social works. Angelo did more than just that while in the seminary; using his very good preaching skills he taught history, patrology and apologetics. It was in the seminary he met the two future saints that would affect his life dramatically. These two Saints were St. Charles Borromeo and St. Francis de Sales, who were both very good pastors in the same seminary, and had a kind of apprentice like relationship. Father Angelo was extremely devoted to Bishop Giacomo until his death in 1914. After Bishop Giacomo’s death, Father Angelo continued teaching in the seminary, but was dragged into World War I and served as a medical corps sergeant and after the war started Italy’s first home for poor young students. His life after the war started changing dramatically, and he even got the attention of Pope Pius XI.