Complex sentence: The victims were South African immigrants who had arrived in Australia 3 years ago from Pretoria, in the hope of a better life for their son, as they felt that South Africa was a too violent place to bring a child up.
Split into simpler sentences: The victims were South African immigrants who had arrived in Australia 3 years ago from Pretoria. They had migrated to hold a better life for their son, as they felt that South Africa was a too violent place to bring a child up.