I recently got an English Bulldog to add to my family. It's something we discussed at length. We wanted to rescue and we let family know we were looking. Well, a dog was located and we were told he was raised with family and around other dogs and that he was very calm. Which he was. And then he started attacking my boxer mix. It doesn't seem to be about anything. Food toys etc. He will just be laying there and his ears go up and his body tenses and he attacks. My boxer is very timid and submissive and is now afraid. Now, it's only been 5 days and I talked to a trainer at our petstore that said to walk them together all the time and keep an eye on them while he adjusts. I just want to do the right thing right away and not have anything escalate further. I'm looking for any advise from those who had similar issues.Both dogs are fixed. Bulldog is 3 and boxer is 4.They are fed and walked on a schedule and working on training with the bulldog. Help?