Four killed after Canberra police chase

Police stopped chasing a stolen car in Canberra's south moments before it ran a red light and hit a vehicle, killing two adults and a baby in the second car.

A 33-year-old Canberra man, 29-year-old woman and her four-month-old baby boy died instantly in the collision on Saturday night, when their car was hit with such force that it slammed into a tree and split in two.

The 23-year-old man driving the stolen Mazda 626 died later at The Canberra Hospital, where his 18-year-old female passenger was on Sunday in a critical condition.

The pursuit was initiated in Queanbeyan shortly after 10pm (local time) after the stolen car sped past police conducting a traffic stop.

The chase continued across the border into Canberra but was called off when the stolen car ran a red light.

A short time later it ran another red light and struck the other car at the intersection of Canberra Avenue and the Monaro Highway exit ramp at Narrabundah.

Police won't say if the chase stopped at a set of lights just 50 metres from the crash scene, or a set of lights further up the road.

The police car arrived at the scene "within a very short space of time", Superintendent Mark Colbran from ACT Policing's Collision Investigation and Reconstruction Team told reporters on Sunday.

Crash scene investigators were at the scene until the early afternoon on Sunday, reconstructing the incident, which will be subject to investigation for the coroner.

Superintendent Colbran could not confirm how fast the stolen car was travelling when the collision occurred, but said the impact had been "very big".

"I've seen worse impacts, but I haven't seen worse results."

NSW Police Commissioner Andrew Scipione said the young officers involved were traumatised by the "tragedy almost beyond description".

"Our thoughts go out to not only those involved in the accident but their families, loved ones, and please spare a thought for those officers involved, he told reporters in Sydney.

"No officer would ever want to go through this - these men were simply doing their job."

Superintendent Colbran also defended the young officers.

"Police don't start pursuits, other vehicles choose to engage in pursuits," he said.

"It's always a very difficult decision that police have to make on the spot, whether or not they should engage in the pursuit or not."

The issue of police pursuits has recently been under the spotlight in NSW, which has developed new laws aimed at cracking down people who initiate dangerous car chases.

The laws, which include five-year jail terms for repeat offenders, were sparked by the death of toddler Skye Sassine who was killed in a police pursuit on New Year's Eve.

- AAP