Several men are seen circling the alleged knifeman, trying to coral him away from others.
Paul O'Shaughnesy's first thought when he saw a blood-soaked man wielding a knife in the centre of Sydney was for the safety of others.
The group then worked together, according to interviews in The Age, to overcome the knife-wielding man. "I want to acknowledge those members of the public who got involved", he said. "More to come." said NSW Police Force on Twitter.
"Those attempts thankfully were unsuccessful", said Supt Gavin Wood of New South Wales Police.
"They were courageous, and and i can only use that word seriously, they were significantly fearless people".
'So insane! A random dude just started stabbing people in the city right outside where we were having lunch, ' @JackHuddo said on Twitter.
NSW Police have set up a series of roadblocks in the area.
"A number of crime scenes have been established and a number of road closures are in place, which is believed to have significant impact on traffic and public transport this afternoon".
A woman's body has been found in a building in central Sydney after a major police operation shut down part of the CBD. "I saw people running so I ran towards him with a few other guys", Jack Huddo said on Facebook.