An inquest into the brutal Lockhart killings has painted the picture of a family torn apart by a father's depression and the violent fall of a mother into mental illness.

NSW State Coroner Michael Barnes is presiding over the hearing into the deaths of Geoff and Kim Hunt, and their three children - Fletcher, 10, Mia, 8, and Phoebe, 6 - at their family farm in regional New South Wales in September 2014. Ms Hunt and the children all died from single gunshots to the head.

It is believed Hunt shot his wife outside the family home before going inside and shooting the three children dead in their beds, and then driving to a dam on the property and taking his own life.

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An inquest into the brutal Lockhart killings has revealed Geoff Hunt blamed himself for killing wife and young children in a suicide note

The inquest, which is being held in Wagga Wagga - near the NSW-Victoria border, has been told 'no one could have predicted' the family's tragic collapse in the aftermath of a near-fatal car crash in 2012 that left Ms Hart with physical difficulties and a significantly altered personality.

Before the accident she was described by loved ones as a 'warm and loving mother, a perfectionist with lots of energy', according to Counsel assisting the coroner, Peggy Dwyer.

But brain injuries she suffered in the crash left her prone to sudden rage and 'explosive' outbursts.

'On a number of occasions she said she wished she had died in the car accident,' Dr Dwyer said.

Family and friends arrive for the start of the inquest into the deaths of the Hunt family members at Wagga Wagga Courthouse in the NSW Riverina

NSW State Coroner Michael Barnes is presiding over the inquest, which family and friends of the Hunt's are attending

The inquest in Wagga Wagga is scheduled to run for four days

Detective Sergeant Darren Gunn carries evidence relating to the inquest into the deaths of the Hunt family members at Wagga Wagga Courthouse

The inquest also heard Hunt's parents noticed he seemed extremely depressed just days before he murdered his family.

'Geoffrey has no smiles today,' his mother, Lynette, remarked, the inquest was told.

'No,' John, his father, replied. 'He hasn't smiled in a week.'

An inquest was told a note believed to have been left by Hunt read: 'I am sorry, it's all my fault, totally mine'

The Hunt children, Phoebe, 6, (left) Fletcher, 10 and Mia, 8, (right) grew up on the family wheat farm 80km from Wagga Wagga

Jenny Geppert (left), sister of Kim Hunt, arrives for the start of the inquest into the deaths of the Hunt family members

It was also revealed at the inquest Hunt blamed himself for the brutal killings in a suicide note.

'I am sorry, it's all my fault, totally mine,' the handwritten note read, the inquest was told.

The inquest was also told the small farming community was 'shocked and bereft' by the murders.

A visitor to the farm first discovered Kim Hunt and her three children dead from shotgun wounds. Police investigators described the scene as 'shocking and disturbing'

'Each of these deaths left a terrible gap in the lives of family and friends,' Dr Dwyer said.

'They are also confounded as to how this could happen to a loving and gifted family, who had tried so hard to support each other in the lead-up to this tragedy.'

Dr Dwyer also said it appeared the Hunt family was not experiencing financial troubles at the time of the killings.

Geoff and Kim Hunt, pictured together before the brutal murder that shocked Australia

Photographs of the Hunt family - parents Geoff and Kim and their children, Fletcher, Mia and Phoebe - feature on the order of service at the family's funeral last September

The inquest also heard police removed two guns from the property and later returned them in 2013, including a W Cashmore double-barrelled shotgun. It was the same gun used to kill Ms Hunt.

The inquest begins the day after Ms Hunt's sister released a statement on Monday.

Jenny Geppert thanked locals for their support during a ''traumatic year'.

Jenny Geppert kneels beside the coffin of her sister, Kim Hunt, and by those of her nephew and nieces, Fletcher, Mia and Phoebe at the funeral at a football oval in Lockhart, 80km south of Wagga

Kim Hunt, pictured with daughters Mia (left) and Phoebe , was left with a brain injury after a catastrophic cat crash in 2012

'The love and care from our friends and extended family will also be forever remembered,' Ms Geppert said, according to The Daily Telegraph.

'This week will be difficult for our families, another arduous formality to endure.

'We hope that this tragedy may remind all of what really matters in this world and to act with humility and empathy towards others at all times. Thank you in advance.'

The inquest comes after it was reported earlier this year the murders were linked to 2012 car crash.

Stunned and grieving locals gathered on a football oval in Lockhart (above) last September to try and come to tersm with the loss in violent cirumstances of the Hunt family (pictured in foreground)

However, rumours she may have carried about the shooting were dismissed by police.

'There was a a lot of talk about that story going around, but it wasn't based on anything but conjecture. It appears that [the father Geoff Hunt] was responsible,' an investigator told Daily Mail Australia at the time.

Detectives have also investigated the family's financial records and an alleged suicide note left by Hunt.

*Anyone who is suffering from depression or mental health issues should contact Lifeline on 131 114 (Australia) the National Suicide Prevention Lifeline on 1800 273 8255 (USA) or the Samaritans on 08457 90 90 90 (UK), or a local help group.

A police vehicle guards the entrance to the Hunt family property last September while detectives gather evidence at a gruesome crime scene which shocked officers and ambulance workers who attended