A MAN has died as the result of a confrontation with police officers at a home on Sydney's northern beaches.

Police were called to a granny flat in Ingleside just after 9.35pm on Saturday on reports of a domestic-related incident.

Officers attended a granny flat attached to a property on Mona Vale Rd and were allegedly confronted by a man armed with a shotgun.

He is said to have pointed the firearm at the officers and threatened them.

Police then shot the man in the leg.

Acting Assistant Commissioner Julie Boon told reporters on Sunday that the man was armed and pointed the unregistered shot gun at officers. Police then fired one round at the man's leg, she added.

The 53-year-old man was taken to Royal North Shore Hospital in a critical condition, where he died a short time later.

A critical incident investigation has been launched.

"Police applied first aid, before the 53-year-old man was treated by NSW Ambulance paramedics and taken to Royal North Shore Hospital in a critical condition, where he died a short time later," NSW Police said in a statement.

"A crime scene has been established at the home which will be examined by specialist forensic officers."

"We are very concerned for the welfare of the three officers involved and appropriate action will be taken to support these police," Ms Boon added.

Photos from the scene showed an engagement party sign out the front of the property, sparking questions over whether the man was attending the event.

However, a NSW Police spokesperson told news.com.au that the property has separate accommodation at the back, which is where the man was staying.

Police were called to the home on the back of the property, which is where the domestic-related incident allegedly occurred.

The incident was not affiliated with the engagement party that was taking place at the time.

It is unclear whether the man had any relationship with the people at the front of the property.

At this point police are investigating the incident and trying to determine how the man obtained the shot gun he used to threaten officers before being shot.

"A Critical Incident Investigation Team from the State Crime Command's Homicide Squad will now investigate the circumstances surrounding the incident," NSW Police said in a statement.

"The investigation will be subject to independent review.

"All information will be provided for the information of the Coroner.

"No further details are available at this time."