Police aren't ruling anything out in their investigation into the death of Hamilton man John Isaac.
His body was found in the Waikato River near the Ngāruawāhia boat ramp last Thursday evening, just hours after Detective Inspector Darrell Harpur believes the 52-year-old fell victim to foul play.
Waikato Police are seeking the public's help, asking for anyone who witnessed unusual activity on the banks of the river anywhere from Hamilton CBD to Ngāruawāhia on January 18.
"It was an incredibly hot day and there was plenty of people on the river," Detective Inspector Harpur told Newshub on Wednesday.
"There were fisherman, swimmers, people in sea-biscuits - there must have been plenty of people that must have seen something."
Detective Inspector Harpur described Isaac as a "big man" who had a number of health challenges and often stayed home.
When he did venture out in the central city he would often ride his black bike and visit local shops.
Isaac was a father of three. His elderly father is still alive and he also had a granddaughter.
Police say he suffered a violent death.
While Detective Inspector Harpur wouldn't confirm how Isaac died, he says there are people out there who have the details.
"We are in the early stages of our investigation; we've completed the post-mortem and the results are that John died a violent death.
"He was put in the Waikato River but he hadn't been in the river long."
Over the weekend, police announced Isaac's body had been found by members of the public out on their boat.
"The men who located him did an outstanding job by getting Isaac to the riverbank at Ngāruawāhia, where a police boat and search and rescue team were able to recover him," Detective Senior Sergeant Ross Patterson said on Saturday.
But how he came to be in the river remains a mystery for the roughly 20 detectives dedicated to Operation Angelo.
After falling victim to foul play earlier on January 18, police say his body may have been dumped in the river any time after 3:30pm, before he was eventually discovered at 6:30pm.
"It's a classic whodunit really", Detective Inspector Harpur said on Wednesday.
"All possible scenarios are on the table.
"We are asking for any sightings of anything that looked out of place or unusual on the banks of the Waikato River, particularly from Hamilton CBD right down to Ngāruawāhia."
Things that could be considered unusual include vehicles that may have been parked close to the river, or people who may have looked out of place.
The detective inspector wouldn't be drawn on how many people could have been involved, instead saying there was a "large pool" of persons of interest - and again adding that John was a "big man".
"He was 193cm, probably around 100kg and of medium to solid build."
Police are particularly interested in any suspicious activity at bridges over the river.
"There are a number of access points under those bridges, including a number of laybys and places where people could actually pull up in a vehicle."
Detective Inspector Harpur said as of Wednesday morning, police had limited leads but reiterated the importance of keeping an open mind.
"The worst thing you can do is suffer from tunnel vision.
"We have some time that we need to account for, we'd like any sightings of Isaac, whether he's been at any or shops or general sightings in the area."
He was last seen wearing black cargo pants and a green camouflage pattern t-shirt, with a gas mask image on the front.
Isaac's tangi was held in Titahi Bay on Wednesday and police are continuing to support his whānau.
Waikato residents can expect to see an increased police presence near the river while inquiries are carried out.
Anyone with information is asked to call 105, or make a report online at 105.police.govt.nz, clicking "Update Report" and referencing file number 240119/8775.
Information could also be provided anonymously to CrimeStoppers by calling 0800 555 111.
