'Hero' Bystanders Risk Lives To Stop CBD Stabber

Police have praised the "significantly brave" members of the public after a man allegedly stabbed a woman in Sydney's CBD.

Members of the public performed a citizens arrest on the man after he had allegedly stabbed the woman on York Street, shortly after 2pm on Tuesday.

Video captured by witnesses showed the man shouting as he wandered through the streets, at one point climbing on top of a car and waving a knife in the air.

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People brandishing chairs and a milk crate were among those who chased the man and restrained him until authorities arrived, with police praising the bystanders as "heroes".

"I want to acknowledge those members of the public who got involved. They were brave and I can only use that word seriously," Superintendent Gavin Wood told reporters.

Video from witnesses shows one man attempting to subdue the alleged offender, chasing him along the road with a chair. Other members of the public, one armed with a crowbar, also attempted to stop the man, as he ran through the streets.

Members of the public managed to perform a citizens arrest, using the chair and crate to hold the man in place until police arrived.

Photo: Twitter @johnnie_txt

Paul O’Shaughnessy helped chase the alleged offender down with his brother Luke.

"We both ran after the guy, and got a grip of him as well as we could," he told reporters.

"We managed to retain him, there was another guy who put a crate on the guy's head."

Prime Minister Scott Morrison has also praised the "brave actions" of the people who detained the man until authorities arrived.

"The violent attack that took place in Sydney this afternoon is deeply concerning," he tweeted.

"The attacker is now in police custody following the brave actions of those who were present at the scene and were able to able to restrain him."

Labor leader Anthony Albanese also praised "the amazingly brave bystanders".

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"Very scary visuals. The fact people were putting their own lives on the line by taking action, was an act of incredible bravery and I certainly pay tribute to them," he told 10 News First.

"Certainly this was a scary incident."

Social media is already lit up with people praising the actions of "milk crate man" and the man with the chair.

Firefighters from the NSW Fire and Rescue arrived on the scene to help and held him down until police arrived.

The man's clothes can be seen covered in blood as he holds his blood-soaked hands to his face.

Wood praised the "significantly brave people" who put their own lives in danger to perform the citizen's arrest.

"To approach a person with a mindset of obviously what this person did, with clear evidence of a stabbing previously, these people are heroes," he said.

"The arrest of the offender happened in very close proximity to where I stand where a number of members of the public physically restrained the offender.

"These people are heroes."

The man was then arrested by police and taken to Day Street Police Station.

A woman has been taken to Sydney Hospital in a stable condition after being stabbed in the back during the attack.

Main image: Twitter @johnnie_txt