To be the honest me, I think the police has no choice but to restrain from using deadly force or even any force at all when they are totally outnumbered by a crazy mob even unarmed. This does not need any high-ups. If you hit one guy with a baton you got ten punch you down and one kick to the head or neck may kill you. If you shoot one person, the other 10 or 100 may rip you in pieces before anybody can help you. Number is always the king.
On the social media, lots of sentimental mocking of "not shooting the trumpsters, but police not hesitate to kill if they are black". But I think the police will restraint even when the rioters are black WHEN outnumbered by 100 times, without automatic rifles and armored vehicles. The bottom line is everybody is emboldened when there is no consequence.