So did the Shepard have any injuries (from the other dog)?
Other stories indicate this may have been a privately owned dog run ~ part of an HOA.
That's possibly why the cops won't bring charges ~ they are waiting on the HOA President to bring charges ~ which I would have no problem doing.
It's obvious the cop violated the rules, and went further and violated some of the implied rules by shooting another resident's dog.
There will be some lawsuits.