Other police killed marchers and bystanders at a parade in the Ponce massacre (1937). The Nationalists believed these showed the violence which the United States was prepared to use in order to maintain its colonial regime in Puerto Rico.[35] Historians Manuel Maldonado-Denis and César Ayala believe the motive for this repression, especially during the Great Depression, was because United States business interests were earning such enormous profits by this colonial arrangement.[35][36]