Armed police officers were called to the Pak'nSave carpark on Mill St just after 1pm today after a person was reported to be in the area with a gun.
Nearby workers were shocked to see an armed police officer running across Ulster St towards a man, woman and child standing by their bus in the car park at about 1.20pm.
A police media spokesperson said police were called to the carpark after the people were unhappy after being asked to leave by a nearby retailer.
The group was standing near the group of shops housing The Helm bar, St Pierre's Sushi, The Cheesecake Shop and Subway.
The person was reported to have a gun, but early reports suggested it may have been fake.
One person was arrested and the rest of the group left on foot, the spokesperson said.
One worker told the Herald she was pulling out of BP on Ulster St about 1.20pm when a police officer carrying a large rifle ran across the road and jumped over a bush before reaching the people
There were nine police officers, all armed with tasers, and three police cars.
The armed police officer ran across the road towards the people who were standing near a bus parked near The Helm.
Another worker said the officers looked extremely serious and the officer was pointing the rifle down as he ran across.
They saw the woman put her head out of the white bus to speak with police before she stepped outside it.