The couple were in the campervan when the alleged gunman fired a number of shots into the vehicle after 2am on Friday.
Hours later, at approximately 8 a.m. local time, police discovered McKinnon's body inside of the van in the village of Gordonton, located almost 75 kilometres from Raglan.
While Bianca Buckley was able to escape and call police, her 33-year-old Australian fiance, Sean McKinnon, was seriously injured.
The arrest followed a manhunt for the suspect after the 33-year-old victim was found shot dead in a camper van in Raglan, in the Waikato region.
The search for the suspect in New Zealand comes nearly a month to the day since the deaths of three people in northern B.C., which would in turn spark a Canada-wide manhunt for Bryer Schmegelsky and Kam McLeod, who were both found dead last week.
They want to hear from any witnesses who saw the campervan after the shooting - and Det Insp Pitkethley expects someone knows who killed Mr McKinnon.
Police said the attack was believed to be "random".
Corangamite shire councillor Simon Illingworth told regional paper The Standard that the Port Campbell community was shocked and saddened by the musician's death.
"They're dedicated and they worked throughout the night to hold this person to account", Pitkethley said in a press conference.
"I can not even begin to understand what she's gone through as a person".
'They're young. They're still at that great age where that reckless temperance of youth hasn't come into line with the responsibilities of adulthood and it never will for Sean now, ' Emmeline said.
McKinnon was from southwest Victoria. He said police were supporting the woman, who was "very shocked and distressed".
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A former RCMP deputy commissioner pointed out some striking resemblances between the case in New Zealand and the one that unfolded across Canada, which drew global attention.
"It is understandable and concerning to have an armed offender outstanding, but I want to reassure the public that we are working hard to identify and locate the offender".
This type of thing, he said, presents a huge issue for police.
Waikato Police revealed on Facebook that they responded to a serious incident in Raglan at 3.20am.
"They do have a lead and they're looking for a vehicle at the moment".
His body and the stolen vehicle were found at Gordonton, 80km away from the crime scene, about 8am on Friday.
Anyone with information is asked to contact Hamilton Police on 07 858 6200 or anonymously via Crimestoppers on 0800 555 111.
A file photo of a white 2017 Toyota Hiace ZL.
"Police are conducting inquiries to establish the circumstances".
"Owing to our privacy obligations we will not provide further comment".
A homicide investigation into the campervan shooting is ongoing.