The incident unfolded at about 5 p.m. as an officer was working off-duty at Ross Dress for Less at 301 Pike St., said Detective Renee Witt of the Seattle police.
The officer received reports of a disturbance outside the store and then saw the end of what appeared to be a fight between two men. The officer went outside and one of the men told him that the other man had pulled a gun on him.
The suspect with the gun began walking away from the scene. The officer attempted to stop the suspect, but the suspect fled on foot.
Bicycle officers immediately responded to the area and saw the suspect running south in the 1300 block of 3rd Avenue. Due to the time of day, the area was heavily congested with commuters waiting for buses.
Officers were able to catch up to the suspect and quickly take him into custody without risk to pedestrians. A loaded pistol was found in the suspect's front pants pocket, Witt said.
Officers determined that the suspect is a convicted felon with outstanding misdemeanor warrants from King County. He was booked into King County Jail for investigation of violating the Uniform Firearms Act.
The other man involved in the fight left the scene before officers could talk to him.