The two men involved in the robbery are on the run.
Police want to hear from anyone who saw anything suspicious in the area between 2.30pm and 5pm yesterday. They are still seeking sightings of the Subaru.
The snatch happened about 2.30pm yesterday near the Dominos Pizza and the Northland Regional Council carparks on Water St.
One man had the gun while a second involved in the robbery was the getaway driver of a stolen vehicle which was found abandoned on Raumanga Heights Drive an hour after the hold up.
The vehicle, a black Subaru Forrester, was stolen from Second Ave earlier in the day. Police would not say how much was stolen in the robbery.
An Armourguard employee, who was returning to a company van after collecting cash from the regional council, was confronted by a man wearing a balaclava.
Police say a pistol was pointed at the male guard who handed over the bag containing an unspecified amount of money before the robber ran to a waiting car, which then sped off up Maunu Rd towards Maunu.
A short time later Raumanga Heights Drive was cordoned off and members of the police Armed Offenders Squad were called to the scene after the getaway car was found.
They approached the car with firearms ready but found the vehicle empty. A police dog and handler scoured the area but were unsuccessful in picking up a scent.
A team of police were also called to Kereru St in Maunu. Roadspikes were laid out as police stopped one vehicle and identified a property in the street which they later entered to speak to residents there.
A woman from the car that had been stopped was arrested on an outstanding warrant and taken to Whangarei police station. She was not related to the robbery.
People in nearby Puriri Park Rd were perplexed by the police activity.
"What's going on with all these police?" asked one woman.
Police were also looking for a second car, a grey Ford Falcon, believed to have been linked to the robbery.
Earlier, detectives spoke to a handful of people in the Dominos and the council carpark.
Whangarei District Council's Water St carpark entrance was briefly blocked as detectives carried out preliminary enquiries.
Two women believed to have been witnesses to the robbery were driven away in a police car.
Late yesterday, police were still looking for the two robbers.
Anyone who saw the getaway vehicle around Whangarei between 7.45am and 3.30pm yesterday should contact Whangarei police on 09 4304500.