Context: In 1744 in what is now the province of Bohol, what is known today as the Dagohoy Revolt was undertaken by Francisco Dagohoy and his followers. This revolt is unique since it is the only revolt completely related to matters of religious customs, although unlike the Tamblot Uprising before it, which was not a complete religious rebellion. After a duel in which Dagohoy's brother died, the local parish priest refused to give his brother a proper Catholic burial, since dueling is a mortal sin. The refusal of the priest eventually led to the longest revolt ever held in Philippine history: 85 years. It also led to the establishment of a free Boholano government. Twenty governors-general, from Juan Arrechederra to Mariano Ricafort Palacin y Abarca, failed to stop the revolt. Ricafort himself sent a force of 2,200 foot soldiers to Bohol, which was defeated by Dagohoy's followers. Another attack, also sent by Ricafort in 1828 and 1829, failed as well. Dagohoy died two years before the revolt ended, though, which led to the end of the revolt in 1829. Some 19,000 survivors were granted pardon and were eventually allowed to live in new Boholano villages: namely, the present-day towns of Balilihan, Batuan, Bilar , Catigbian and Sevilla .

Question: What did Dagohoy's brother do that was considered a sin?

Answer:
duel