I have had a sheep farm a few years ago, and I have had coyote attacks. They are very bad, claw marks on the side of my sheep, parts removed on the hind quarters. I think if your dogs did do the damage they would have had blood on them for sure! It doesn’t sound very good for you, specially she is a vet and he is a sheriff. I understand and I am almost positive with that kind of damage to the llama they would of had to have blood stains on there mouth, somewhere. Couldn’t they have investigated more? Sounds like they were at the wrong place at the wrong time.