Complex sentence: Residents in Northern District then initiated the "Liberate Sheung Shui" campaign in September 2012, when angry citizens gathered outside Sheung Shui East Rail Station and protested with slogans and banners.
Split into simpler sentences: Residents in Northern District then initiated the "Liberate Sheung Shui" campaign in September 2012. Citizens gathered outside Sheung Shui East Rail Station and protested with slogans and banners.