Sydney, Australia - Australian police have identified a 40-year-old man who suffered from mental illness as the perpetrator of a shopping center stabbing rampage that killed six people and left several more in a critical condition.

New South Wales police Assistant Commissioner Anthony Cooke said Sunday the man had come from the northeast state of Queensland and was known to law enforcement.

"There is still to this point nothing that we have, no information we have received, no evidence we have recovered no intelligence that we have gathered that would suggest that this was driven by any particular motivation ideology or otherwise," said Cooke.

"We know that the offender in the matter suffered from, suffers from, mental health."

The 40-year-old man – who was shot dead by an officer at the scene – was named as Joel Cauchi.

He is believed to have come to Sydney a month ago and hired a small storage unit in the city. It contained personal belongings, including a boogie board.

Among Cauchi victims was a nine-month-old baby – said to be in a "serious but stable condition in hospital" – who was saved by being handed over to a stranger by her fatally wounded mother, Ashlee Good.

"The baby got stabbed," one man at the scene with his brother told Channel 9 News in the aftermath of the attack. "The mom got stabbed and the mum came over with the baby and threw it at me."

Other stories of courage emerged from Saturday's attack.

Lone senior police officer Amy Scott is being hailed for tracking down and then shooting dead the assailant during his killing spree.

One young man was filmed fending off the attacker on an escalator, armed only with a bollard, while storekeepers opened their doors to shelter frightened shoppers.