Sixtus II was elected pope in August 257, at the beginning of the persecution of Valerian. Within a year — on August 6, 258 — he was seized by imperial agents while celebrating Mass in the Catacomb of Pretextatus and beheaded on the spot with four of his deacons (Januarius, Vincent, Magnus, and Stephen). The seventh deacon, Lawrence, met him on the way to martyrdom; Sixtus prophesied that Lawrence would follow him in three days, which was fulfilled.
The shock of the murder of a pope at the altar of his own Mass — together with his deacons and many companions — reverberated across the Christian world. His name appears in the Roman Canon of the Mass.