A 32-year-old man allegedly went back to his car to get a shotgun after an altercation outside the Work and Income office in the Christchurch suburb of Linwood.
All Work and Income offices in the greater Canterbury area were put in lockdown as the incident unfolded at about 8.45am today, a year after two staff were killed at the Work and Income office in Ashburton.
The Linwood Work and Income office was open but the man did not enter it, Canterbury police commander Superintendent John Price told media.
A security guard and Work and Income staff were involved in an altercation with the man.
He went back to his car, got a firearm and presented it outside the office.
Supt Price believes the weapon was not fired.
Five to six police cars searched for the man and he was found at 9.15am in Ferry Rd near the intersection with Ensors Rd.
He was arrested without incident after a short foot chase.
He did not have the gun on him at the time of the arrest but it was located later.
It is believed to be a shot gun.
The man will appear in Christchurch District Court this afternoon on firearms charges.
"I want to thank the prompt action of the Work and Income staff for alerting police and ultimately this led to a very quick and safe arrest," Supt Price said.
Police are now visiting all the Work and Income offices in the Canterbury district to reassure staff.
"I want to reassure the public and all people in Canterbury it's about not tolerating this sort of behaviour and ensuring when people behave in this way, and use firearms, then we will hold them to account," Supt Price said.
Security was tightened at all Work and Income offices after Peggy Noble and Leigh Cleveland were killed when a gunman opened fire in the Work and Income office in Ashburton in September 2014. Lindy Curtis, who was shot in the leg, was seriously injured.
"Everyone has a right to be safe and feel safe whether at home or at work," Supt Price said.