Sean McKinnon, 33, and his Canadian sweetheart Bianca Buckley, 32, were parked on a beach in the town of Raglan around 3:20 a.m. when a man thumped on the window, The Australian reported.
Police said Mr McKinnon was sleeping in the campervan with his fiancee when the alleged gunman fired a number of shots into the vehicle after 2am on Friday.
The van was discovered around 8 a.m., about 46 miles away in the village of Gordonton - with McKinnon's lifeless body inside, according to the report. The Canadian woman managed to escape and run away, and called police.
"In light of the current circumstances, a general arming order for police staff is in place this afternoon for the entire Waikato District and will be reassessed later today".
As for the victim's identity, police said they would not be naming him until a formal identification has been carried out and his next of kin have been notified.
McKinnon, 33, grew up around Warrnambool in Victoria's southwest.
"This is a random attack by what we attribute to a sole offender", he said.
Friends are remembering him as a talented musician, an avid surfer and a "genuine, gentle man with a heart of gold".
Another friend Julian Smith told AAP McKinnon was a "lovable, knockabout Aussie guy" who loved his surfing.
"Consular officials in Wellington, New Zealand, have offered consular assistance".
Corangamite Shire Mayor Neil Trotter said community members were stunned by Mr McKinnon's death.
"She is obviously shocked and traumatised", Detective Inspector Graham Pitkethley told reporters on Saturday.
"I just cannot believe that such a nice person could have their life finished like this", said Simon Illingworth, who'd surfed with McKinnon for 15 years in his native Australia.
One lone male is being sought in connection to the "random attack", Pitkethley said, according to The Australian.
When they refused, McKinnon was shot dead.
"This is a tragic incident", he said, adding that investigators were providing the female victim with the "support and welfare" she needs.
Det Insp Pitkethley confirmed armed police were involved in the manhunt.
Witnesses had come forward to help police find the man, he said.
"If you think you have seen this vehicle or have information that may be helpful please contact Hamilton Police on (07) 858-6200".
Police are expected to brief media on the investigation on Saturday morning.
"We are appealing to the public for any sightings of a white 2017 Toyota Hiace ZL van (registration KWF362 - similar to the attached photo) travelling between Raglan and Gordonton before 8am this morning".