Super sad but kind of odd. If your German Shepard has been with you for so long, they know what you like or care for. Animals feel that. Especially a solid dog like a German Shephard. When my grandpa passed away he was very sad. One year on the exact date (Grandpa's death anniversary) he just went crazy. Not crazy violent but just wouldn't stop running around and barking. Sadly we had to put him down at that point . . . I don't think your dog killed those goats. I don't believe it. Do you have any proper evidence of that?