"We're being traumatised." Waleed Aly on the footage of the Sydney CBD stabbing.

Journalist Waleed Aly says the great amount of footage that surfaced within moments of the Sydney CBD stabbing on Tuesday afternoon is “traumatising”.

One woman was killed and another seriously injured in the rampage, allegedly perpetrated by a 20-year-old man who has been identified as Mert Ney.

Numerous videos of the man’s attack emerged on Twitter including footage, belonging to Seven News, that followed the man – wearing a top stained in blood – jumping on top of a car and waving his kitchen knife.

The Project Panel on the Sydney CBD shooting. Post continues after video.

Other vision shows the moment he was apprehended by bystanders, who used a chair and a milk crate to restrain him before the police arrived. One man can be heard screaming at the suspected murderer: “They are people you just stabbed… I’ll kill you right now”.

Discussing whether the footage being posted to social media is a “good thing or a bad thing” on The Project, Carrie Bickmore said, “It must obviously help with investigations and stuff, but seeing it all unfold … I don’t know”.

“I do feel like we’re being traumatised by watching it,” Aly said of the footage.”I’m not sure that trauma helps us in any way, does it really? Can you think of a way it would?”

Aly also reflected on what he would do had he been a bystander witnessing the crime, saying he isn’t sure he would be as brave as the men who have since be hailed as “heroes”.

“As I was watching the vision, I tried to imagine myself in it and I don’t think there is any chance of me approaching,” he said.

“Like you say, you don’t know until you’re in it, but I can’t imagine myself doing it.”

On Tuesday night in a press conference, NSW Police Commissioner Mick Fuller praised the members of public who apprehended the accused attacker.

"Three members of the public, who can only be described as heroes of the highest order, have engaged this 21-year-old man and have placed him essentially under arrest even though he was brandishing a large butcher's knife and was clearly dangerous," he told reporters.

Superintendent Gavin Wood of NSW Police similarly labelled the members of public as "heroes".

"They were brave and I can only use that word seriously. They were significantly brave people.

"To approach a person with [this] mindset ... with clear evidence of a stabbing previously, these people are heroes."