This happened yesterday.
Hong Kong police fire gun and use water cannon on protesters
Water cannons are one thing, and those are already bad even when it's used in Western countries because of the risk for injuries out there. But pointing loaded firearms at a crowd and firing warning shots are a no-no in any playbook on crowd control. Furthermore, there's that one cop kicking a protester who was sitting on the ground. Finally, they also arrested a 12-year-old in that. Obviously, nothing to rebuild any form of trust between police and protesters.