and cockers aren't the only breed to 'suffer' from 'rage syndrome' - springers, golden retrievers, papillions have also been reported cases.
It is likened to a type of fit or seizure, since the dog in question has no 'recollection' of the event, somewhat like an epileptic fit. In which case good breeding techniques and practices help keep such genetic mishaps from hopefully occurring.
Sorry, this is a bit off topic, but what you say in your comment above about other breeds struck a cord - our last dog, Cassie, a golden retriever suffered from epilepsy (sadly, she is now at the bridge) Her seizures were classic, normal seizures, but last year she had a strange one - she showed all her usual signs of an on coming seizure, but then just got aggressive, backing away from me, barking, growling and baring her teeth at me. We were out in the garden at the time, and when she started lunging at me, I made a hasty retreat into the kitchen and watched from the window. After a few minutes, in which she continued to bark and growl, she stopped and then went into her normal post-seizure actions. I wonder if that was similar to 'rage', although she only ever had one like that.