Boy witnessed fatal shooting inside Quakers Hill police station

Police say a young boy witnessed the fatal shooting of a knife-wielding man who stormed inside Quakers Hill police station earlier today.

The boy, believed to be aged 12, was in the foyer of the north-western Sydney station when a man rushed in carrying a large knife and started screaming, the Sydney Morning Herald reports.

The man, who was said to have been aged in his 40s, then lunged towards an officer before he was shot with a single shot in the shoulder.

Police have no idea why a man walked into the premises and allegedly started threatening officers.

He is yet to be identified, but police say today’s incident is not believed to be terrorism related.

A sergeant with 24 years' experience fired the fatal shot around 10:40am, with the altercation lasting just seconds, Assistant Commissioner Denis Clifford told reporters outside the station.

"There was a shot fired by the sergeant. It struck the man. He was rendered assistance but passed away a short time later," Mr Clifford said.

He said police "have no idea of the motive" of why the man entered the station.

"I can say that a large knife has been located at the scene and obviously that will be part of the investigation and the crime scene unit are on the scene now to try and piece together what occurred."

No officers were injured in the confrontation.