After the man had been Tasered, the member of the public helped Mr Gurney to handcuff the man.
Haast Rural Fire Party chief Kerry Eggeling said up to six volunteers turned out to help.
"He was on his own and we do help out in situations like that," Mr Eggeling said. "I believe he Tasered the man. That would be the first case of someone being Tasered in the Haast."
Mr Eggeling said the Haast community was very supportive of its policeman and was always ready to support him when called upon.
He said the incident was not unprecedented.
"Years ago we had a policeman here who got beaten up."
Previous Haast constable of 18 years, Robin Manera, regularly called on the community to help him, from apprehending deer poachers to assisting with road blocks to stop people on the run.
Mr Gurney recently returned to South Westland after several years as the sole officer at New Zealand's most remote police outpost, in the Chatham Islands.
He had previously served in South Westland at Franz Josef and Whataroa, and took over from Mr Manera at Haast last month.
At the time he told the Hokitika Guardian that he enjoyed the challenge of remote rural police work and was not fazed by it.
"Some police officers don't like it because there is no immediate back-up and you're by yourself, but I enjoy that. It keeps me on the ball," Mr Gurney said.
Late yesterday morning he was busy dealing with a fishing boat drifting off Jackson Point and in danger of hitting rocks.
West Coast acting area commander Inspector Iain McKenzie said the response from Haast community members in coming to the aid of Mr Gurney was outstanding.
"Constable Gurney has significant experience as a sole-charge officer in remote communities so he certainly knows how to manage these situations," Mr McKenzie said.
He "made a good call" in ensuring he had back-up before approaching the alleged offender.
"The outcome was a credit to everyone involved and I can't thank those community members enough for their response," Mr McKenzie said.
Grant David Sadler, 52, made a brief appearance in the Greymouth District Court yesterday morning before a Justice of the Peace.
He faces two charges of assaulting a police officer, one charge of assaulting a female, and the intentional damage of a police car.