Sorry to hear about this. Losing birds for any reason is bad enough, but losing them like this is sickening.
Too late to help the birds you lost, but you can do something about any birds that remain, or new birds you will get to replace these. An electric fence. They are not difficult to install and are highly effective. Video below is a good example of what is needed, how to do it and if you stick with it to the end, how a fence works. Imagine yourself, or better yet, a dog or other varmint taking his place. Not many animals come back for a second dose:
I'm sure you will also get suggestions to shoot these dogs and it is understandable to think that way and to even want to do it. But that is after the fact.
If a person has a fence like this up, it may save the birds and prevent having to go on a bad dog hunt......again after the fact. I"m suggesting this not only for Aggie, but for anyone else with birds who would like to prevent this type of fate for their own birds. Dogs and other predators can be shot, but are easily replaced by more dogs and other or different predators. Electric fences work and repel most of them. Shooting is a short term solution to a long term problem. A really hot electric fence is the long term solution.