This would be a Cop on Cop shooting and execution of the canine by medical staff.
The LE dog was deprived of his Civil Rights under Color Of Law.
If you make it a legal issue, I believe the human officer was involved in self-defense.
Makes you wonder however, if an officer had to kill the dog for self-defense, what about civilians.
Because if a dog is capable of murder (see the self-defense defense), then that introduces a whole other ballgame to the dog breed in general.
In my opinion.