Obregón won the 1928 Mexican presidential election, but months before assuming the presidency he was assassinated. Calles' harsh treatment of Roman Catholics had led to a rebellion known as the Cristero War, which broke out in 1926. As an ally of Calles, Obregón was hated by Catholics and was assassinated in La Bombilla Café on July 17, 1928, shortly after his return to Mexico City, by José de León Toral, a Roman Catholic opposed to the government's anti-Catholic policies. Toral was offended by the Calles government's anti-religious laws, which led to the Cristero War by Catholics against the regime. Obregón was not as fiercely anticlerical as Calles and had not imposed the anticlerical provisions of the 1917 constitution when he was president. Toral's subsequent trial resulted in his conviction and execution by firing squad. A Capuchin nun named María Concepción Acevedo de la Llata, "Madre Conchita", was implicated in the case and was thought to be the mastermind behind Obregón's murder.