The gun used was probably a pistol but police would review the in-store CCTV surveillance footage to determine the exact weapon.
Mr Brazier said there were no customers inside the dairy at the time.
Police were still gathering more details from the victim, who was last night being helped by Victim Support.
The dairy was closed after the robbery.
A number of police vehicles were parked up outside the shop and several officers were engaged in patrolling nearby streets.
Mr Brazier said it was not known how the offender travelled to the dairy or whether he fled in a vehicle.
Police were keen to speak to anyone who had been in the area just before or immediately after the robbery.
Staff at neighbouring shops spoken to by the Bay of Plenty Times said they had not heard anything.
A staff member at Otumoetai Veterinary Hospital said they were totally unaware the dairy had been robbed until police cars swooped on the area.
Vet nurse Georgina Williams said a handful of police cars and a police tracking dog turned up at the dairy shortly after the robbery.
Ms Williams said the dairy was run by man who had been there about a year.
She said the block of shops was relatively safe but burglaries happened from time to time.
"Nothing like this has happened here before though," Ms Williams said.
"I'm not too worried, we're pretty far away.
"I'm sure the burglar would have run off in the other direction, usually they rob and run. These things can happen anywhere."
Inside the veterinary hospital at the time was a police officer who was getting his police dog, a puppy, vaccinated.
Ms Williams said the officer was unaware of the incident until he walked out and saw his colleagues,
The puppy was not used in the police response, she said.
A woman living nearby said she had moved into the area only five weeks ago and had visited the shop only two hours earlier to top up her cellphone.
She said she was shocked to learn of the robbery, and had not heard or seen anything. Her immediate thoughts were for the couple in the dairy.
"They are a really lovely friendly couple, really helpful and I hope they are both okay," she said.
It is not the first time Grange Rd Dairy has been held up.
In April 2009, a man armed with a spanner held up the dairy after he had spent all his flatmate's money gambling. He fled with a money tray from the till containing $450.
Anyone with information about the latest robbery is asked to call Tauranga police on 577 4300 or call Crimestoppers anonymously on 0800 555 111.