Dogs may redirect aggression if interrupted in another aggression (i.e. dog-on-dog aggression). The dog may turn and threaten or bite the closest person or animal to them, who are often not involved. These dogs may be non-aggressive in the absence of the interruption of another threat.
However, if it is in response to an individual who was punishing or threatening to him then other aggressions types would have to be considered. It is possible that it could be part of what used to be known as dominance aggression.
**Aggression categories compiled from:
Clinical Behavioral Medicine for Small Animals, Karen L. Overall, M.A., V.M.D., Ph.D. Diplomate, American College of Veterinary Behavior, Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia. Pennsylvania, Mosby, Inc. 1997
The Dog Who Loved Too Much: Tales, Treatments, and the Psychology of Dogs, Dr. Nicolas Dodman, BVMS, MRCVS, Bantom Books, 1997