Redirected aggression. My oldest dog has done this. For example she is barking at the window and another dog approaches, she is mad that the other dog is at the window, but she can't get to it, so she goes for the dog inside that is in her way. I stop her immediately and my two other dogs do not attempt to go near her when she is in this state..they back down and let her have the window. It doesn't happen all the time by any means, but it has happened.
Misty- Samoyed Mix, Tannor- Golden Retriever CGC
Robyn- GSD CGC, TC, Midnite-GSD CGC,TC, Brennan-Golden Retriever CGC, Batman-Husky/Greyhound , Apollo-GSD