Mwanga was a wicked king, and very violent, using his power to try and force the young men into immoral acts. Charles was a catechist, and instructed the young men who were serving in the king's court in the Catholic Faith and he baptized them. He inspired and encouraged his companions to remain chaste and faithful.
Mwanga was a superstitious pagan king who originally was tolerant of Catholicism. However, his chief assistant, Katikiro, slowly convinced him that Christians were a threat to his rule. He convinced the king that if these Christians would not bow to him, nor make sacrifices to their pagan god, nor pillage, massacre, nor make war, what would happen if his whole kingdom converted to Catholicism?
When Charles was sentenced to death, he seemed very peaceful, even cheerful. He was to be executed by being burned to death. While the pyre was being prepared, he asked to be untied so that he could arrange the sticks. He then lay down upon them. When the executioner said that Charles would be burned slowly to death, Charles replied by saying that he was very glad to be dying for the True Faith. He made no cry of pain but just twisted and moaned, "Kotanda! (O my God!)." He was burned to death by Mwanga's order on June 3, 1886. The other young men were martyred in various ways, and together they were canonized by the Church.
O God, by whose providence the blood of the martyrs is the seed of the Church: Grant that we who remember before thee the blessed martyrs of Uganda, St. Charles Lwanga and his Companions, may, like them, be steadfast in our faith in Jesus Christ, to whom they gave obedience even unto death, and by their sacrifice brought forth a plentiful harvest; through the same Jesus Christ our Lord, who liveth and reigneth with thee and the Holy Spirit, one God, for ever and ever. Amen.