To the best of your ability (I know it’s difficult to see), focus on the man’s right arm. He was clearly reaching for his pocket while he was on the ground. The cops told him to stop, and he continued. Does he have to get a shot off before the cops are allowed to respond?
I seem to recall tales of ROEs similar to that for troops in Afghanistan.
If it's good enough for our troops operating overseas it should be more than good enough for domestic law enforcement.