One can argue that the cop should have run away completely if he was capable to but that's just hindsight, one doesn't totally know how everything went down. I feel really bad for the young father... This is just a messed up situation.
Instead he was just tending to the wounded child, the thing the father should have done. I find it difficult to find any fault whatsoever with this cop. He did everything right.
1. Sees kid dart in front of him, slides his bike causing greater injury to himself to try to avoid greater injury to child
2. Injured at this point, starts tending to the child
3. Sees angry father coming at him, he wisely identifies himself as police
(this is where it should stop because attacking anyone who identifies as police is fucking stupid)
4. father, unnamed assailant, 18 y/o cousin all assault the cop, he fires one shot to end it
If the father followed the cardinal rule of not attacking a police officer he'd be alive today. Moral of the story should be never attack someone who identifies as a police officer unless you fear bodily harm/death from said officer.