Complex sentence: When the Colonial Government established Rottnest Island as prison for indigenous people their families would gather on sundays to send signals to those on the island using fire, these fires also aided those who attempted to escape from the Island.
Split into simpler sentences: When the Colonial Government established Rottnest Island as prison for indigenous people, their families would gather on Sundays to send signals to those on the island using fire. These fires also aided those who attempted to escape from the Island.