I think that most chicken owners who came upon their chickens being slaughtered would fight to save their property, be it a gun pitchfork, whatever. It takes alot of time and money to raise chickens, not to mention they are your pets, um twice! Please dont offer to pay his vet bill, not until he offers to pay for all of his dogs destruction. That would be like admitting guilt and tht is not your position. Of course, you wish it had worked out differently but since he disregarded your requests to pen his dog and you were kind enough to not ask for restitution the first time the dog got your chickens, not sure why he should be surprised with the end result. Don't back down until he does. I am sorry this is coming between brothers, tho, it was his choice, not yours. What would he have done if your chickens went in his yard and attacked his dog? I doubt he would have just stood there and let his dog get killed. Its a Knee jerk reaction to guard your property.