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A teenager was stabbed twice, then rolled into a mattress cover and weighed down with two steel bars before his body was dumped in the Clutha River.
Police yesterday named the victim as Michael Anthony Hutchings (18), who had been stabbed once in the stomach and once in the neck.
He was the eldest son of Lyn and Mark Hutchings of Clinton in Otago, who are returning home from a holiday in Australia.
Late yesterday, no formal suspects or a motive had been identified.
It is still not known how long Mr Hutchings' body had been in the water, where he was killed, or what the precise cause of death was, although it is believed his stab wounds led to fatal blood loss.
Mr Hutchings' identity was confirmed after forensic dentistry tests.
In a brief statement, his parents said Michael would be sadly missed by family and friends.
His younger sister, Sarah, said Michael was a protective big brother and always looked out for her.
"I just really want to know what happened to him," she said.
Michael attended South Otago High School, leaving at the end of 2005 to study for some farming qualifications which he achieved at the end of 2006.
It is understood he had been working on a dairy farm for the past year.
No weapon has been found but police forensic staff spent much of their time yesterday at an Old Coach Rd property in Kaitangata where Mr Hutchings had been living by himself.
"We have no idea where he died," Operation Hawk inquiry head Detective Inspector Ross Pinkham said.
Attempts to contact the property owners were unsuccessful, but police ruled them out as suspects.
They, like many associates and friends, had been interviewed.
Forensic staff are expected to continue working at the house today.
Former South Otago High School pupils described Mr Hutchings as a quiet person with only a handful of friends.
He kept to himself and no one spoken to knew of any enemies or who would want to harm him in any way.
Detective Inspector Pinkham said interviews with Mr Hutchings' associates had helped pinpoint his activities in the days before the discovery of his body by an Inch Clutha farmer on Saturday afternoon.
Forensic tests revealed his body had been wrapped in a white mattress cover and lashed to two steel bars about 2.1m long and 16cm wide.
Black nylon braided cord was used to tie the bars to his body before it was taken to the river and rolled into the water.
The farmer who discovered the body, Morris Storer, was in his boat checking stock along the Clutha River. He said it had been a shock to find a body in the river.
"It's not the kind of thing you expect to see in the water, that's for sure."
Mr Pinkham urged the public to look out for each other and to take all the usual security precautions.
