Complex sentence: The brutality of the RCMP in its treatment of the downtrodden protesters provoked a major public outcry, and the day after the riot, ten thousand people turned out to a protest at the Powell Street Grounds (today's Oppenheimer Park).
Split into simpler sentences: The brutality of the RCMP in its treatment of the downtrodden protesters provoked a major public outcry. The next day, ten thousand people turned out to a protest at the Powell Street Grounds (today's Oppenheimer Park).