Hard to really answer as there are many factors that contribute to fights. Couple questions that might help clarify:
-The initial attack: Were both dogs off leash when they met and the attack happened?
-In regards to your dog being aggressive: When this occurred, were both dogs either on or off leash?
-How was your pup socialized during their first year?
-How often does your dog interact with other dogs/animals?
No doubt your dog may be on edge since the attack.
Just out of curiosity, during the initial attack, was the other dogs and owner aware of your dog coming to them before you released?