An A320 First Officer reported noting a 'Smoke Aft Cargo' ECAM after gate arrival. The crew ran the QRC; shot the fire bottle; and decided that normal passenger disembarkation was safe to continue.

Narrative

After shutting down both engines; I observed an ECAM for Smoke Aft Cargo. I alerted Captain to ECAM as we were just beginning shut down flows. Captain directed me to complete QRC actions and informed me he had witnessed a 'puff' of smoke on his side of aircraft. Ground crew had not established communications yet. Along with ECAM; there was an overhead warning light illuminated indicated smoke in aft cargo area. I completed QRC actions including discharge of one fire bottle. After a short period of time; the overhead red warning light for indication of smoke/fire extinguished. Captain was able to establish communication with aft Flight Attendants who also reported smelling an odor similar to smoke. Normal disembarkation by passengers continued as there were no other indications of fire or a problem from either ground personnel or aft cabin Flight Attendants. I contacted ramp personnel to request Fire Department response as a precaution. I was told to 'Stand By'. I then contacted Ground who directed me to contact Tower who switched me to a discreet tower frequency. Fire Department responded very quickly and did a thorough inspection of the aft cargo area before coming up to cockpit to report to us that there appeared to be nothing abnormal in the cargo area. Eventually; several other [company] individuals arrived to be debriefed on the situation. I thought the Captain and I handled the situation calmly; professionally; and in a timely manner. I never anticipated this type of ground emergency happening after the engines were shut down and the passengers had started their deplaning. I think a ground evacuation would have resulted in injuries; so allowing the normal deplaning to [continue] was a good decision.