Complex sentence: The Río Piedras Massacre occurred on October 24,1935, at the University of Puerto Rico, when local police officers confronted and opened fire on supporters of the Puerto Rican Nationalist Party.
Split into simpler sentences: The Río Piedras Massacre occurred on October 24,1935, at the University of Puerto Rico in Rio Pedras. Local police officers confronted and opened fire on supporters of the Puerto Rican Nationalist Party.