"It was very quick. I was very scared."
The man then ran from the store, got into a waiting dark vehicle and sped away.
Mr Zai thought there could have been three other people in the vehicle.
On Monday the 25-year-old was welcoming customers back through the grey folding doors.
The fridges were stocked with milk and the trays filled with fresh bread.
But he admitted he was watching the front door very closely and a little nervously.
"Most people are nice in Jack St. We know them."
He said armed robberies were not just isolated to Whangarei and he believed the police could catch the masked robber.
Since arriving five years ago Mr Zai has toured the country while working and studying to be a chef.
"I had searched the internet and New Zealand is one of the nicest places in the world. Here it is beautiful," he said.
During his first year in New Zealand he studied cooking at the Northland Polytech and then continued his studies in Auckland.
He has worked in a noodle shop in New Plymouth and in Levin worked in a bakery.
During that time he has worked in three different dairies and while Saturday's incident was terrifying it has not tarnished his view of Northland or New Zealand.
"New Zealand is a cool place."
Detective Sergeant Dene Begbie, of Whangarei, said it was a concern when someone brandished a firearm at people trying to make a living.
He said the robber was of slight build and could have been young.