Your position is a judgement as well. Information provided by OP is fragmentary at best, hence my indicating earlier things do not add up. Much of the killing behavior I would not consider unusual with an LGD or LGD cross in a highly confined situation. I and people with working LGD's expect the dog to kill even other dogs trespassing onto their turf. The owners of those dogs are much more likely to be liable when their dogs trespass. That is an issue I have had to deal with as do farmers using LGD's. Where you might get into trouble is saying you are defending a backyard flock that is not considered legally in your jurisdiction as livestock.
The human-aggressive nature of the dog in question is not all that clear as emotions have made assessments of that difficult. That is why I suggested early on having an expert checking the dog first hand. There is a mismatch between what LGD's are often expected to do and what the OP is able to support, regardless the dog needs to be removed from the situation it is in. Part of the dog's breeding just is not being considered as most are trying to pigeon hole it as simply a pet.
Much of this is a consequence of LGD's being pressed into service as pets or where resources simply are not enough for the dogs involved. On the hole, we at this site and others have been promoting use of LGD's too much and the problem is coming back to bite somebody.
Yes, I offered my opinion on the matter, prior to a decision being made by the OP, as did several others. The cross Breed and breed trait have been highly discussed in regards to the behavior, and I did consider it in my opinion, though I didn’t specifically state that, I though it was implied in my commentary on breeds generally considered dangerous and the often unstable nature of hybrids. I don’t believe the OP obtained the dog specifically for LGD purposes, and it killed her flock and her cats as well.
Once the OP made an informed decision, having consulted a local rescue agency with experience in the matter, all our opinions are moot.
I just find it a little callous to restate and plead for sparing the dog and rehoming it when the local rescue and OP have come to the conclusion that in this case it is not feasible or safe.
It’s a LGD Breed crossed with a retriever/sporting breed, it wasn’t properly trained as a LGD, and was most likely sold with the intent of being a pet.
I encourage everyone to thoroughly research ANY dog breed or the parent breeds of a dog before purchasing it. Most dog breeds have been specifically selected, sometimes for hundreds of years, for certain traits pertinent to the work they are intended for. Our border collies herd our sheep well with very minimal formal training on our part, the older dogs actually teach the younger ones, and it’s in their nature. An untrained/unbonded to a flock LGD breed is very dangerous.
Hopefully we can all learn something from this thread, and we should all let the OP move on in peace.
Although the discussion is interesting we should find another thread to have it on out of respect for the OP and her situation and decision.