The manager of Wharenui Swimming Pool and Sports centre said police had first told the centre to go into lockdown at 3.30pm.
She said she had been told police had caught someone in the Wharenui School Grounds.
Police had earlier posted an officer at the swim centre's front door.
"All we heard earlier on was there was a person out there with a gun," she said.
"We had a lockdown procedure so we kept everyone in the building. Because we've got concrete buildings, we felt quite safe."
Shortly after the incident on Matipo St, police received another report of a man presenting a firearm toward another person on Riccarton Rd shortly after 3.30pm. No shots were fired.
The man then left in a vehicle. Officers along with the AOS located and arrested the man at an address on Fitzgerald Ave.
The police spokeswoman was unable to confirm if a firearm was located at that incident.