 While all other candidates from the Rome diocese were ordained in the Basilica of St. John Lateran , Pacelli was ordained a priest on Easter Sunday , 2 April 1899 alone in the private chapel of a family friend the Vice @-@ Regent of Rome , Mgr Paolo Cassetta . Shortly after ordination he began postgraduate studies in canon law at Sant 'Apollinaire . He received his first assignment as a curate at Chiesa Nuova . In 1901 he entered the Congregation for Extraordinary Ecclesiastical Affairs , a sub @-@ office of the Vatican Secretariat of State . 
