For one, the officer here, as far as we know, has not been charged with “failure to maintain control of a motor vehicle”.
The prosecuting attorney would surely hit that charge (among others) on any non-government employee who struck the child.
Prosecutors don’t get involved unless there is suspicion that a criminal act has occurred. “Failure to maintain control of a motor vehicle” sounds like a citation that might result in a fine and a stint in Traffic School.