Police say a child ran to ask for help after their mother was killed, as a potentially armed man remains on the run.
Officers say the child ran 400 metres to a neighbour after the alleged attack in the NSW Hunter Valley near Sydney last night.
Passers-by stopped and called police.
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The alleged attack happened in Kearsley, in Cessnock about 7.30pm yesterday.
"It was a traumatic incident as you can imagine, quite horrific for the family members all involved, her two adult children, one young child, so quite horrific," Superintendent Steve Laksa said.
Police say a gun was fired at the property.
They are searching for the woman's partner, Christopher James McLoughney, 37, who they say may have a gun.
McLoughney and the woman had been in a relationship since June this year, Laksa said.
Police believe he may in be in Cessnock, the Lower Hunter or Newcastle.
"Police believe this person may have crucial information in relation to the offence that was committed there last night," Laksa said.
"We just ask the community to provide any information they have in relation to him.
"I'm sure there would be someone out there who knows where he is, or may know where he is, we just call upon those people to give us call and provide their details or anonymously."
He is known to police and is white with short ginger hair, a thin build and is 175 -178cm tall.
The victim is the 58th woman alleged to have been killed in a domestic violence attack in Australia this year.
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