That is a shame. They should of tried to catch the dog via a catchpole (I think thats the name, it's a lead on a pole) or a trap or something.

Worse case scenario should of been that the dog go through a quarantine process.

I'm not defending the police officer or anything and I don't even agree with it but here it is illegal if a dog chases deer. So illegal that is legal to shoot any dog who is caught chasing deer. I don't know if they have the same rule there or not.