Outside, Kim Hunt, 41, lay dead on the garden path. Inside, her three children, Fletcher, 10, Mia, 8, and Phoebe, 6, lay dead in their beds. In a nearby dam, police found the body of Geoff Hunt, 44, along with a shotgun.

Mr Hunt most likely killed his family before killing himself in September last year, the Wagga Wagga Local Court heard on Tuesday.

"Each of these five deaths left a terrible gap in the lives of their family and friends," counsel assisting the coronial inquest, Peggy Dwyer, said. 

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

The "truly tragic" killings took place on the family's "Watch Hill" property near Lockhart, in south-west NSW. 

Dr Dwyer said witnesses reported seeing Mr Hunt in different moods the day before the bodies were found. Mr Hunt's parents said he appeared affectionate and attentive with the children. But his mother noted: "Geoff had no smiles today."

The court heard Mr Hunt was making plans shortly before the killings. He had agreed to attend a meeting of local grain growers on Tuesday, the day the bodies of his wife and children were found. He had made plans to play tennis the day after that.

But the court also heard a brain injury Mrs Hunt sustained in a 2012 car accident had put significant strain on the family. Witnesses are expected to describe how Mrs Hunt was often left angry and unable to filter her thoughts after the accident.

"The person who bore the brunt of the injury was Geoff," Dr Dwyer said. "A number of witnesses saw Kim verbally abuse her husband over sometimes minor matters."

Several times Mrs Hunt was heard to say she would have been better off dying in the accident. The couple attended counselling, on their own and together.

Two guns Mr Hunt kept at the property were confiscated by police after Mrs Hunt reported suicidal feelings, Dr Dwyer said. But police returned them once her condition improved. One of these guns, a W Cashmore double-barrelled shotgun, was the gun used to kill her.

Mrs Hunt's body was found covered with a jacket. The children were wearing the same clothes they had been seen in the night before.

Detective Sergeant Darren Gunn, the officer in charge of the investigation, said each person had died of a single gunshot wound to the head. He also said Mr Hunt appeared to have taken his own life. 

The inquest continues.

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