Cash was handed over and the man ran out of the shop, he said.
Police were not prepared to disclose how much cash was taken or the contents of the note.
The police armed offenders squad was called to a nearby house and searched for an alleged offender but no arrests were made.
The robber is described as a light-skinned male Maori aged between late teens to early 20s.
He is of thin, lanky build.
The checkout operator was unhurt, but extremely shaken and upset. Mr Hayes said police were working on a number of lines of enquiry.
Meanwhile, police are yet to arrest anyone in a heist last year when it took two minutes for gun-toting robbers to terrify staff and rob the same supermarket of thousands of dollars.
The brazen robbery happened just before 10pm closing on August 21. Police said as the last shoppers, a couple, left the store, the darkly-clothed trio slipped through the main door, which could be opened only from inside.
Once inside, the three walked past a Lotto desk and then ran at three staff members near the checkout area.
One of two robbers, brandishing a pistol, swore at the staff and demanded money as the employees, two women and a man, were forced at gunpoint into the office.
The third robber was armed with a hunting knife, about 30cm in length.
Two other staff members, in the rear of the supermarket, escaped through a door to a nearby business and raised the alarm.
The detained staff members, were forced, at gunpoint, to hand over three bank bags full of cash.
If anyone has any information about the latest robbery they can contact Detective Pete Hayes, phone 09 430-4500 or anonymously through Crime Stoppers on 0800 555-1111.
