On June 17, 1970 Harvey and Jeanette Crewe were gunned down in the living room of their Pukekawa farmhouse and dumped into the nearby Waikato River.
Fifty years on, theories still swirl around the whodunnit, which has been the subject of two trials, a Royal Commission of Inquiry and a
Crewe cold case: Fifty years and no answers in infamous Pukekawa whodunnit
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There was no sign of his daughter or her husband Harvey.
But there was blood - pools and splatters and dragmarks in various places.
Demler could hear his 18-month-old granddaughter Rochelle calling out and raced into her bedroom, to find her lying down in her cot.
The toddler was not crying or upset - but she was filthy.
Her cot reeked of urine and excrement and she clearly not been cared for for quite some time.
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Demler, strangely, left Rochelle in the cot and drove to his own house, where he called a transport company to cancel a stock transfer, saying Harvey was not home.
He then drove to his neighbour Owen Priest's home.
"There is blood all over the place and I cannot find them anywhere," Demler said.
He asked Priest to come back with him to the bloody crime scene, where he lifted Rochelle from her cot and took her to the home of a friend.
By then, the little girl was cold and crying.
Her eyes were bloodshot, sunken in their sockets and her lips and mouth were very dry.
It was only then, an hour and 20 minutes after Demler first went to Jeanette and Harvey's place, a call was made to the Tuakau police.
So began a 50-year-old murder mystery that would see charges laid, evidence planted, convictions quashed and reviews into the police handling of the case.
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There have been a number of suspects over the years - including Demler, his other daughter Heather, other local farmers, other members of the Thomas family - but no other arrests.
Many central to the investigation have died and those closest to it are not fond of revisiting it.
Pukekawa farmer Arthur Allan, who was convicted of the murders at two trials and spent almost 10 years in prison before he received a pardon, isn't keen on speaking about the case these days.
He has discussed it when needed, but is now "pretty private" and tries to keep out of the spotlight when it comes to this case.
Rochelle Crewe - now 51 - feels the same about speaking publicly aroudn the anniversary.
The murder of her parents is not something she wants to dwell on.
Thomas' brother Des has spent much of his life fighting to clear his family's name and has vowed to keep "fighting" until he gets answers - and vidication.
But he said this milestone anniversary was more about the death of a young couple.
"We need answers. All we want and require is to take the 'who' out of whodunnit'," he said.
"But at the end of the day, this is about the brutal murder of two people in their own home, who were then chucked in the Waikato River like they were just some dead farm animals.
"That's bloody disgusting."
It was evident from the outset that something terrible had happened in the Crewe house.
Blood and bodily fluids stained the chair where Harvey, 28, usually sat and pooled on the carpet beneath and there was a long drag mark down the middle of the living room floor.
The was also blood on the brickwork near the front steps and in the kitchen - on the linoleum floor, the cupboard doors, the hot water tap, on two saucepans.
Police knew they were looking at a homicide -but, with no trace of Harvey or Jeanette, it was hard to say whether it was a murder suicide, home invasion or something else.
Despite extensive searches of the Crewe property and over large areas of surrounding farmland there was no sign of the couple.
Then, almost a month to the day the bloody scene was discovered, two whitebaiters chanced upon Jeanette's body floating in the Waikato River about 9.7km downstream from the Tuakau bridge.
She was wrapped inside a bedspread from her own home and copper wire was found around her legs, where police believed a weight had been attached.
She had been killed with a single .22 calibre bullet to the head.
On September 16 Harvey's body was found, snagged among weeds in the same river about 5km downstream from the same bridge.
He had also been killed by a single bullet to the head.
Harvey's body had been weighed down with an axle - an item of evidence that would prove to be highly contentious over the coming years.
After analysing all of the information from the crime scene, witnesses and post-mortem examinations, police established the couple had been shot dead in their living room between 7pm and 9.30pm on June 17.
They had last been seen alive at 2.30pm, at a stock clearance sale in Bombay.
It's thought they headed back to Pukekawa late afternoon and their car was seen parked on the side of the road 2km south of their home at about 5.10pm, presumably as Harvey shifted sheep or tended to stock in a nearby paddock.
The night of the murder Jeanette fed Rochelle and put her to bed, then served dinner - flounder, potatoes and peas.
After eating Harvey then moved to his armchair and Jeanette to a sofa on his left.
She was knitting - a jersey for her husband - when the killer confronted them.
Police believe Harvey was shot first from behind, by someone standing in the kitchen or just outside the open louvre window.
The shot to the left side of his head, just above his ear, would have killed him instantly.
The killer then advanced into the lounge.
"It is likely that Jeanette verbally challenged the offender in some way, possibly by screaming or shouting," police would later say.
Jeanette was struck in the face and then at some point her head hit the front left corner of the hearth, which would have incapacitated her and left her lying prone on the carpet.
There, she was shot at close range in the right side of the head.
The killer - or killers - then set about dragging the bodies out of front door, leaving Rochelle in her bedroom just metres from the exit.
The gory scene went unnoticed for five days despite a number of people coming and going from the Crewe property, including the delivery man and stock agents.
As the search for the missing couple continued police spoke to neighbours, family, the community and people who thought they had seen the Crewes.
Neighbour Julie Priest - the wife of Owen who went to the house initially with Demler - told the cops she'd heard three gunshots on the 17th, probably after 8.30pm.
Bruce Roddick told police he saw a woman outside the Crewe house in the days between the murder and Demler finding Rochelle.
The theory fast became that she was an accomplice to the killer and snuck back to the house to care for baby Rochelle.
Medical opinion was divided on whether the toddler was fed during those days, with some saying she could have survived without food or water and others saying she certainly must have been tended to.
This sighting has never been independently confirmed, nor has the woman ever been identified.