A gardener who butchered his three children, wife and mother-in-law has today pleaded guilty to their murders.

Anthony Harvey, 24, used knives and a blunt instrument to butcher his family at his home in Bedford, Perth last year.

He killed three-year-old Charlotte, two-year-old twins Alice and Beatrix, and their mother Mara, 41, on September 3.

Harvey then murdered his wife's mother, Beverley Quinn, 73, when she came to visit the next morning.

He lived with the bodies for five days before turning himself in.

Cradling his newborn daughter in his arms, Anthony Harvey looked every bit the proud father as he gazed at the baby girl he killed three years later

Anthony Harvey (pictured with his wife Mara), 24, used knives and a blunt instrument to butcher his family at his home in Bedford, Perth last year

He killed three-year-old Charlotte, two-year-old twins Alice and Beatrix (pictured), and their mother Mara, 41, on September 3. He then murdered his wife's mother Beverley Quinn (pictured), 73, when she came to visit the next morning

Harvey pleaded guilty to the murders when he appeared in Stirling Gardens Magistrates Court on Wednesday via video link from prison. Pictured: The scene of the crime

Harvey, who owned a francise of lawn-mowing service Jim's Mowing, pleaded guilty to the murders when he appeared in Stirling Gardens Magistrates Court on Wednesday via video link from prison.

He will face a sentencing hearing in the West Australian Supreme Court on June 21.

After the murders, Harvey stayed with the bodies for the next five days, before driving 1,400km and handing himself in to a police station in the Pilbara region.

Western Australia Police Commissioner Chris Dawson said the adults were killed in the kitchen, while the children were attacked in other rooms of the house.

Mrs Harvey's sister, Taryn Tottman paid tribute to her and said she 'loved being a mum' and that her daughters were her world.

'She was so proud of each of them and was doing a great job of raising them. Her girls were her world,' she said at the time.

After the murders, Harvey stayed with the bodies for the next five days, before driving 1,400km to a police station in the remote Pilbara region. Pictured: His mother in law

Western Australia Police Commissioner Chris Dawson said the adults were killed in the kitchen, while the children were attacked in other rooms of the house. Pictured: Harvey and his wife Mara

In moving obituaries, she promised to tell her young daughters Phoenix, Sienna, and Ava all about their aunt, cousins, and grandmother.

'You had three beautiful children who you adored and would have done anything for. You were a great mum,' she wrote of her sister.

'You also had a special bond with our mum, which now will never be broken. I will always miss you and I will let your nieces and nephew know all about you. I love you, big sister.'

Ms Tottman wrote emotionally about the last hug she got from her quiet but 'cheeky' niece Beatrix.

'You were always a bit cautious but when you were comfortable the hugs would flow and I will always cherish the last hug,' she wrote.

'It was the longest heart melting hug I have ever had. Our family play dates will be greatly missed. We love you Beatrix and your cousins will always know you.'

Her twin sister Alice was remembered for being daring and adventurous in everything she did.

Flowers left by a member of the public are seen outside the home where the killings happened

Harvey (pictured with wife Mara) appeared to be a doting father, often seen by neighbours happily playing with his children in the backyard of their three-bedroom home

'The more dangerous it seemed to us the more chance there was of you giving it a go,' Ms Tottman wrote.

'As a twin to Beatrix you always had a friend, but would happily play with your cousins on our play dates.

'I will always miss our play dates with your cheeky smile and no fear attitude. We love you Alice and your cousins will always know you.'

Ms Tottman wrote that Charlotte's life was 'way too short' but brought a smile to many people with her happy personality.

'You were a bubbly, energetic, little girl that would make friends wherever you went,' she wrote.

'Watching you and Phoenix together on our play dates was always so entertaining. You were great together.'

The grieving daughter described the agony of losing Ms Quinn, who was killed beside the body of Ms Harvey in the kitchen after she arrived on the morning of September 4.

'There are no words to describe the pain we are feeling after your life was suddenly taken from you,' she wrote.

The Harveys met in 2013 while working at the Sino Steel mine site on Cape Preston, in northwest Western Australia.

They got married in November 2015, months after Charlotte was born on February 4, 2015. The twins followed on July 27, 2016.

Harvey appeared to be a doting father, often seen by neighbours happily playing with his children in the backyard of their three-bedroom home.

The only problem appeared to be that their Jim's Mowing franchise was 'slow' and not making enough money, friends told Daily Mail Australia.

Ms Harvey was then forced to get a nightfill job at Coles and put a unit in Maylands up for sale in January - which failed to sell.

But up until the deaths, Harvey carried on the business as usual, even apparently completing two jobs just hours after Ms Quinn was killed.

Jim Penman, the managing director of Jim's Mowing, said Harvey gave no hint of financial or emotional problems.

Looking back at records, Mr Penman said Harvey sent two quotes to clients at 6.21pm and 6.37pm on that Monday night, less than five hours before he killed his wife when she got home about 11pm from a nightfill shift at Coles, where she worked for at least eight months.

'Those quotes are striking to us. Highly courteous and well-mannered but they were sent just before and then suddenly five hours later they're dead,' Mr Penman said.

He said Harvey had two jobs assigned to him for last Tuesday, the day he killed Beverley Quinn, and the clients never complained they weren't done, so he assumes they were carried out.

'Anthony was telling us repeatedly that everything was fine, he was going well, had plenty of work and enjoyed what he was doing,' Mr Penman said.

Mr Penman did say several franchisees who knew Harvey commented that he had 'extreme mood swings' that could 'go up and then very down'.