At that point you should have called the police. However, that form of stupid over reaction does not excuse you allowing a dog off a lead. If it was an accident, fine - did you offer to pay the farmer damages (as you should have) for any and all damage done? Did you apologise profusely for your pet threatening his livelihood? You took your pet onto his land, you failed to control it and that threatened his ability to pay his bills. In that you were very wrong and irresponsible. If he threatened you as you say, he was also very very wrong and irresponsible. One phone call to the police would have had his shotgun certificate revoked.
He had the right to shoot your dog since, by your own words, it could not be stopped from attacking his stock by other means. He had no right to threaten you or your partner and he should have been prosecuted.
He had the right to shoot your dog since, by your own words, it could not be stopped from attacking his stock by other means. He had no right to threaten you or your partner and he should have been prosecuted.