Last week in southern Flordia, a 76 year old police officer was shot dead by a criminal who had been sentenced twice to life sentence.
Police officers are at risk of very violent crime, so they must use maximum but reasonable force to protect themselves and others.
We should wait for investigation before any comment whether the guangzhou police used excessive force.
The key is in North America, we have an independent investigation mechanism (SIU in Ontario) to perform the investigation. In Guangzhou, probably the local police will investigate themselves, without an arm's length.