They had protesters directly in front of them (which was taken into custody) which was a focus due to the threat they were facing. The cop in charge called it in and got aid to the old man. The cop got suspended without pay. The full video shows he acted responsibly.
Its funny. My wife is Eastern European. She personally took part in the peaceful protests that was the first domino that caused the wall to fall. All of her community of eastern European community as a whole are aghast at the leftward socialist/communist movement in the US they are seeing. The exact same type of government they either escaped before or helped change within to a democratic state. Now they see themselves living in a country that is trying to GO BACK TO a type of government that forced them to protest/escape in the first place.
Federal power to quell a protest in any jurisdiction in the United states is limited by the Posse Comitatus act and limitations of federal power in the constitution.
Option C - Call on congress to pass a law making it a federal crime to cause the death of any individual in police custody, who is incapacitated, to die due to inaction or direct action against that person.
The Czech and Slovak people peacefully protested the Communist government and that lead to the collapse of the Communist Governments all through eastern Europe and lead to a (for the most part) peaceful transition to democracy.
https://en.wikipedia.org/wiki/Velvet_Revolution
That is the model that protesters here in the US should follow.
Destroying businesses and infrastructure only creates more division... which may be the goals of those that are instigating the violence.