Complex sentence: The inmate then alerted former police officer Clarence Dongail to enter the cell and told them to stop, however upon returning to the common area to watch TV, Tony Co attacked Dongail, triggering the riot.
Split into simpler sentences: The inmate then alerted former police officer Clarence Dongail, who entered the cell and told them to stop. However, upon returning to the common area to watch TV, Tony Co attacked Dongail, triggering the riot.