You said bull terrier, I'm going along with you on bull terrier. You're starting to be contradictory here. You want to be specific as to bull terrier vs. pit bull terrier. Then you want to call them "mutts". And now you're going with "dachshund".
They're some form of bull terrier mix with some dachschund in there. It's probably not the dachshund parts that led to this mauling. I'm going to gamble that it's the bull terrier elements.
Feel free to argue otherwise but since I've never read of a violent dachshund attack and I've read of plenty of bull terrier attacks, you should know that I'm going to disagree with you.