A grandmother has been killed in the home she had lived in for as little as two months in an “abhorrent” shooting that left the family property riddled with bullets.

The killer remained on the run on Tuesday, with authorities hunting for the person behind the overnight attack in Ambarvale on Sydney’s south-west outskirts.

Police said three people got out of a dark-coloured sedan on Wednesday night and fired shots at a house on Dickens Road where the 65-year-old woman lived.

Emergency services were called to the property about 11pm and treated the woman, but she died at the scene.

Two other people in the home, a 21-year-old woman and a 34-year-old man, were not injured.

Police said the attack was targeted but were unclear if the dead 65-year-old, who was inside the house when the gunmen took aim, was the intended victim.

The occupants of the house, who authorities believed had lived there for six to eight weeks, were known to police.

Detective Superintendent Grant Healey said police had been unable to interview some distraught family members and they would give them more time to process the death.

“It’s abhorrent, somebody coming up to a house and putting shots off is totally reckless and the consequences are catastrophic,” he said.

“Some members of the family are speaking to us and helping us out, but it’s tragic … your mother and the grandmother to your children has been shot by cowards that stood out the front of the house.”

The force was confident it could rule out family violence as a motive.

Nearby resident Louise Hoser said she heard gunshots shortly after 10.30pm.

“Within 20 minutes I went to bed and my bedroom just lit up with the police lights … they didn’t have the sirens going, but there was a lot of police presence and ambulances up there,” she said.

“I woke my house up to alert them that something was happening … it was very distressing to hear the family, and shocking to find out she was an elderly lady.”

Local officers and the homicide squad are investigating, with police vehicles clustered outside the property on Tuesday as the probe began.

Police inspected bullet holes on the house’s front wall and on stairs leading to the front door.

At least three bullet holes could be seen on the house, while about 10 yellow evidence markers were spotted at the taped-off road as police hunt for the killer.

Officers also crawled underneath a P-plated car parked in the property’s driveway.

Along with the two uninjured occupants, police said the public would be key to their investigation and ask witnesses to contact Crime Stoppers.

Hoser, who has lived in the area for 18 years but did not know the dead woman, said the violence was “part of living on Dickens Road”.

“Every few weeks there’s a lot of police presence,” she said.

“Dickens Road always gets the negative [attention] but we do have some really nice people that live on Dickens Road, and in Campbelltown in general.”

-AAP