The next day, it is alleged, Mr Harvey murdered his wife's mother Beverley Quinn at the family home.

Mrs Quinn, 73, had been visiting the house regularly to support her daughter and three grandchildren, neighbours said.

Just hours before Mrs Harvey and her three children were allegedly murdered, work emails from Mr Harvey's Jim's Mowing franchise were being sent out.

Mrs Harvey and her husband were behind a 'Morley south' franchise in Perth.

A friend of Mrs Harvey had told Fairfax Media she had supported her husband financially in setting up the franchise venture.

There are almost 4000 franchisees Australia wide attached to the business, which has since become known as Jim’s Group.

WAtoday has obtained copies of two work emails sent from Mr Harvey's work email account.

The emails were sent out at 6.21pm and 6.37pm Perth time on September 3.

The brief emails provided quotes to clients for work required at their respective homes.

Jim's Group managing director Jim Penman said he was "appalled" and "stunned" by the events which had taken place.

"Its unbelievable we don't know how to cope with it ...it's really horrifying," Mr Penman told Fairfax Media on Wednesday.

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"We are just trying to understand this whole thing."

In a Facebook post published on Tuesday, Mr Penman said the Jim's Group community had been left devastated by the deaths and would be offering counselling to any and all franchisees.

"We are also looking at tightening the requirement for franchisees to keep in more regular contact with us. We will do everything we can to prevent such a horrifying event from ever happening again."

Police Commissioner Chris Dawson has revealed police will allege knives and a blunt instrument were used in the murders.

Police are also alleging Mr Harvey remained at the property for days after the murders before he made his way to the state's north where he was later arrested and charged, Mr Dawson said on Monday.

"We are still working through a number of timelines but we are going to be alleging that he remained at the house for some days and then made his way to Pannawonica," Mr Dawson said.

Mrs Harvey has been described as a devoted parent by her sister Taryn, who penned a heartbreaking tribute to her, her three nieces and her mother Beverly Quinn.

Taryn released a written statement on Monday saying Mrs Harvey "loved being a mum and she loved her girls".

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"She was so proud of each of them and was doing a great job of raising them. Her girls were her world," the statement read.

"This world is a sadder place with the loss of these five beautiful people but Heaven has gained five new angels."

A Go-Fund me page aiming to raise $35,000 has been set up to help the family with funeral costs.

The page has already raised more than $5000. Click here to donate.