Police are "urgently" seeking public help to catch the person who killed Auckland entomologist Stephen Thorpe, while the victim's friends are mourning the "tragic" loss of a "tolerant and knowledgeable" man.
Thorpe was a keen entomologist who had been working at an office beneath the Blockhouse Bay Tennis Club for a number of years.
He died from critical injuries late on Saturday morning.
Police said the person responsible left the scene on foot.
Jacqui Knight, from the Moths and Butterflies of NZ Trust, said she had known Thorpe for about 10 years as the trust had a butterfly habitat very close to the tennis club.
Knight described him as being "very tolerant and knowledgeable" of anything to do with insects, which were his passion. He would go on daily walks through the reserve by the club, searching for insects and plants, she said.
"He spent seven days a week at the office - he just loved it. He was a loner who kept to himself most of the time and wouldn't hurt a fly. It's just so tragic this has happened."
On Saturday morning, Knight, who lives in Blockhouse Bay, said she had been at the supermarket when she heard a helicopter circling near the tennis club.
"I got a phone call telling me not to go to the butterfly habitat because there'd been an incident nearby, so I stayed away until that afternoon when I decided to check on a new plant I'd recently planted."
When Knight arrived, she was surprised to see the area was still cordoned off by police and she was not allowed to go through.
"I started worrying then because I knew my friend was there every day and I didn't know where he was."
By that evening, Knight said she was becoming more and more stressed as she could not get in touch with her friend and no one else had heard from him either.
"I didn't sleep much that night so in the morning I went down there again and that's when police confirmed to me he had been killed."
Thorpe had no close relatives living in New Zealand as far as Knight knew, and had originally been from Australia.
"He was so well-spoken and just loved the nature here, he was very successful at what he did too and had quite a few insects named after him I believe."
Knight said she last saw her friend a week or so before his death as she had asked him to help her with her page on the website iNaturalist, which he used frequently.
"He loved that site - he had about 900,000 specimens listed on there."
A police spokesperson said they wanted to hear from anyone who saw anything suspicious happening in the area, and in particular in Rathlin Street, on Saturday.
"We urgently need information from the public that could assist police. We are eager to gather any CCTV, dashcam or security footage from the Blockhouse Bay area, [from] around 11.30am."
On Sunday, a scene guard remained in place at the park and extra officers were patrolling the suburb while investigators went door-to-door to speak to residents.
Police were using metal detectors and could be seen digging through nearby piles of mulch.
A post-mortem examination and formal identification are being carried out.
Information could be provided through the police 105 line, on their website police.govt.nz, with the file number 240824/4136, or anonymously through Crime Stoppers on 0800 555 111.