Why bring up ACAB in this situation? The police were not involved in either side of the shooting. Per the article’s description the rifleman pulled out a rifle and appeared to be readying to fire before a protest peacekeeper (not police) shot and injured him using a handgun. Unfortunately in the cross fire one protester was killed by the peacekeeper but it looks like this prevented a potential mass shooting event.

This source is including many more causes of death not included in the US number. The average annual direct killings by the US police is 1096 (33.1 per 10 million), while the UK is 3 (0.5 per 10 million), about 66 times worse per capita.