Oh I am so sorry for you. This exact same thing happened to my niece and nephew just about a month ago. They had taken their german shepherd and jack russell terrier out to Pittsburgh to see my other niece and had given the GSD a sedative for the long ride. When they got to Pittsburgh they all went to a park for a walk. The GSD tore into the jack russell and seriously injured her (they thought she might not live but thankfully she did) and she also bit a man in the park. She was put to sleep the following day. My niece and nephew were so traumatized by seeing it happen right in front of their eyes. We are sure it had something to do with a reaction to the sedative but the vet suggested she be PTS and so she was. ((((Hugs)))) to you as I know a little of what you are going through. What a tremendous shock!