Detective Sergeant Glenn Restieaux said there was a possibility the sole offender, who was wearing dark clothing, may have been loitering around the back of the station leading up to the robbery, waiting for the right moment to strike.
"He's gone in and was carrying what we believe was a machete and he's thrown a bag at the attendant and demanded cash and cigarettes."
Mr Restieaux said the most concerning aspect happened seconds later when the offender lashed out at the attendant - possibly because he was slow to react to his demands.
"It was not a full-out attack but he has struck him on the arm." He said that while the cut was not serious the attendant was understandably left shaken.
At that stage a member of the public walked in and the robber grabbed what he could and ran off across Taradale Rd toward Trinity Cres.
"We are not sure at this stage what he managed to get away with," Mr Restieaux said.
The attendant was assisted by the man who had walked in after he called police, who were quickly on the scene and set up cordons in the immediate area as well as in Kennedy Rd. "He did a great job."
About the same time the offender was seen running into Trinity Cres, a black car which had been parked there was seen being driven away toward Kennedy Rd.
"We are not sure whether it is related to this or not and we would certainly like to hear from the driver."
Police want to hear from anyone who may have seen the darkly clad offender in the area of the service station in the time leading up to the robbery or afterwards.
Mr Restieaux echoed recent comments from his colleagues about the rise in robberies.
"It is very concerning."
In the past couple of months there had been robberies at Hastings bars Zabeel's and The Horse and Hound.
The Te Awa Dairy in Napier South had also been targeted and shortly after that a man was mugged and robbed near the central city.
Waipawa's Four Square superette had also been struck by robbers.
