Police say the man they will interview over the discovery of a woman's body in the boot of car in Christchurch and an attack on two tourists on the West Coast had lived with the person found dead.
A 38-year-old man was arrested about 3am on Monday after a five-hour standoff near Fox Glacier in relation to the homicide and attack on the tourists.
The body of Amy Elizabeth Farrall was found on Sunday afternoon in the boot of a car at a New World car park in Christchurch suburb of Woolston. The 24-year-old had been reported missing on Saturday.
Detective Senior Sergeant Darryl Sweeney told Radio New Zealand's Checkpoint programme on Monday that Miss Farrall and the man had lived at the same house for a short time and police are trying to determine exactly what relationship they had.
Police are appealing for any sightings of another vehicle believed to be involved - a dark-coloured Nissan Terrano that travelled from Christchurch to the West Coast late on Saturday morning.
The hitchhikers - a 28-year-old German and a 27-year-old of Japanese and Dutch origin - were picked up on Sunday afternoon in Whataroa, about 30km north of Franz Josef, by a man driving a blue Terrano.
Police said when they were found near the side of the road near Franz Josef about 4pm, the German woman was stabbed in the neck, while other women had suffered a broken pelvis.
They had been initially treated at Grey Base Hospital, but were transferred to Christchurch Hospital on Monday night. The German is in a serious but stable condition, while the other woman is in a stable condition.
The man remains in custody on the West Coast and is bring treated for injuries, including dog bites, at Grey Base Hospital.
The family of Amy Farrall say they are shattered by her death. In a statement released on Monday afternoon, they say she loved her animals and was always helping people in need. The family are requesting privacy and time to grieve and to process what has happened.
Miss Farrall worked as a community support worker at Richmond Services Ltd, a non-government organisation providing disability and mental health support services in Christchurch. Chief executive Barbara Disley says she was a valued staff member.
Five-hour standoff after pursuit
Police say that as soon as the hitchhikers were found they saturated the surrounding area with all available staff and road blocks were put in place on State Highway 6. A helicopter and a fixed-wing aircraft were also sent to the area.
A patrol located the Nissan Terrano near Sugar Loaf Road, south of Fox Glacier, shortly before 8.30pm on Sunday. Police said failed to stop and a 90-minute pursuit ensued that ended at a road block at Karangarua River, 25km south of Fox Glacier, about 9.50pm.
Armed staff then surrounded the vehicle and began negotiating with the driver. Meanwhile, Armed Offenders Squad members from Tasman District, Dunedin and Christchurch were flown to the area by helicopter to assist.
Superintendent Richard Chambers says it was a volatile situation, as the man threatened to douse his vehicle and himself with petrol and was also throwing Molotov cocktails at officers. They did not know if he was otherwise armed. The standoff lasted more than five hours before the man was overpowered about 3am and taken into custody.
Community disbelief and shock
Westland mayor Mike Havill says the community is in disbelief at the brutality of the attack on the hitchhikers. West Coast Tourism chief executive Jim Little says operators are appalled that two people who came to enjoy the area were savagely attacked.
Mr Little says thousands of tourists hitchhike along the long stretch of South Island coast each year without incident and it's one of the safest places in the world to catch a lift. Some operators are raising money for the injured women, he says.