A New South Wales man whose main intention was suicide, also killed his wife and children because he believed it would "[spare] them future pain", a coronial inquest has been told.

Kim Hunt, 41, and her children Fletcher, 10, Mia, 8, and Phoebe, 6, were found dead on their farm in Lockhart in September 2014.

The body of 44-year-old Geoff Hunt — Kim's husband, and the children's father — was found a day later in a nearby dam. A gun was found beside his body.

All were killed with single gunshot wounds.

Coroner Michael Barnes is hearing evidence about the deaths at Wagga Wagga Coroner's Court.

A forensic psychologist from NSW Police told the inquest she thought Hunt's main intention was suicide, but he believed his wife and children were dependent on him and so in killing them he was "sparing them future pain".

Dr Sarah Yule said she believed Hunt loved his wife and children.

"He had a level of dependency on the family unit," Dr Yule said.

She said she believed there were "several indicators" that Hunt was depressed in September 2014.

Dr Yule said some people with depression will "go to considerable lengths to conceal what they're feeling", to hide their mental condition from family or friends.

A forensic psychologist said she believed Geoff Hunt was depressed. ( supplied )

"He presented a facade of being able to cope. It couldn't get better. He couldn't fix it," Dr Yule said.

She said his use of a gun and a single injury indicated he did not intend to inflict pain on his wife and three children.

Yesterday, the coroner heard from the last person to see the Hunt family alive.

Lorraine Bourke was employed to help the Hunt family with domestic chores after Ms Hunt sustained permanent brain injuries in a 2012 car accident, which the court heard led to a significant change in her personality.

In September last year, on the night Hunt is believed to have shot his wife, three children and then himself, the mood in the house was tense, Ms Bourke told Mr Barnes.

Ms Bourke discovered the body of Ms Hunt outside the house the next day. Police later discovered the children's bodies inside the house.

On Tuesday, the inquest heard a handwritten note found in the home read: "I'm sorry, it's all my fault, totally mine."

The note did not identify the author, although a handwriting expert told the court she was "very confident" Hunt wrote it.

The inquest is continuing.