An elderly man who pointed a gun at police officers outside a home in Sydney's south and shot another person in the head has killed himself during the standoff.

Police were called to a domestic dispute at a house at Engadine this morning after neighbours heard a gunshot.

The incident comes on White Ribbon Day, which aims to end violence by men against women and girls.

Police said the elderly man, who did not live at the property, fired at the front door of the Ridge Road home, leaving the 56-year-old son of his estranged partner with grazing on his forehead caused by shrapnel.

Five ambulances blocked access to the street and paramedics treated the 56-year-old for minor injuries.

Acting Assistant Commissioner for Central Metropolitan region, Karen McCarthy said police responded to reports of shots fired at about 7:00am, but when they arrived the elderly man pointed a gun at police.

He was treated by paramedics but died at the scene.

A critical incident investigation of the circumstances surrounding the shooting and the standoff with police officers is underway.

"Obviously this was a high-risk situation for the police as they responded," she said.

"The firearm was pointed at police and unfortunately the person did suffer a self-inflicted injury."

Two teenage children and a woman were also at the property during the incident, but were uninjured.

Acting Assistant Commissioner McCarthy said the family was not known to police.

"It is a tragic event," she said.

"Obviously it is White Ribbon Day today and it's just a reminder of the violence that is still present in our community and how as a whole community we need to remain vigilant and continue to work together to address this problem," she said.

Neighbour 'saw a body fall to the ground'

A woman, who did not want to be identified, said she knew the family who lived at the house where the shooting happened.

"I know the mum quite well and they are a lovely family — my daughter goes to school with one of the youngest boys, who I think is about 14 — the other boy is a bit older," she said.

"When I heard the gunshot, I thought it was a door slamming from the wind or a car backfiring — it's really sad to hear that it was a shooting."

Another man called Jack, who lives down the road, said his mother was on the front lawn when she saw a man fall to the ground.

"She said there was a bit of screaming and she saw a body fall to the ground," he said.

"I'm really shocked to be honest. I can't believe something like this has happened in this area."

Forensic police are examining a grey ute on Ridge Road, while police continue to doorknock local residents in the area.

Neighbours said an elderly woman recently moved into the house after fleeing domestic violence.

Editor's note (23/11/18): This article has been edited after it incorrectly stated the man's estranged partner had been killed during the incident.