English Springer Spaniel
English Springer Spaniels, and their smaller cousin the Welsh Springer Spaniel are gun dogs from the isles of Great Britain. They are closely related to the Cocker Spaniel - so much so that Springers and Cockers were sometimes birthed from the same litters. The breeds have differentiated more over time. English Springers are still used as gun dogs around the world. The show line is susceptible to something called "rage syndrome" which is a behavioral condition where aggression might emerge suddenly, but it is actually very rare. If your Springer is exhibiting unusual aggressive behavior, investigate changes in it's health or environment before assuming the worst.