Do you have a legit source for this? When I search for information, I only found this case, “Luo Changqing, a 70-year-old Hong Kong cleaner, died from head injuries sustained after he was hit by a brick thrown by a Hong Kong protester during a violent confrontation between two groups in Sheung Shui, Hong Kong on 13 November 2019.”
None of the other legit sources claim the police killed any of the rioters.
Many countries in the SCS are doing this. In fact China was late to the game, as Vietnam did it much earlier.