Joel Cauchi, 40, killed five women and a male security guard at a Westfield shopping centre in Bondi Junction on Saturday afternoon before being shot dead by a female police officer.

On Monday morning, New South Wales Police Commissioner Karen Webb was asked by the Australian broadcaster ABC about footage of the massacre that appeared to show Cauchi targeting women.

She replied: "The videos speak for themselves, don't they?"

"It's obvious to me, it's obvious to detectives that seems to be an area of interest that the offender had focused on women and avoided the men.

"Five of the deceased are women and the majority of victims in hospital are also women.

"We don't know what was operating in the mind of the offender and that's why it's important now that detectives spend so much time interviewing those who know him, were around him, close to him, so we can get some insight into what he might have been thinking.

"We won't know necessarily but we have to take a judgement from those who know him."

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Cauchi suffered from mental health issues, police have said, and investigators are not treating the attack as terrorism-related.

His victims were Ashlee Good, 38, Dawn Singleton, 25, Jade Young, 47, Pikria Darchia, 55, and security guard Faraz Tahir, 30. The sixth victim has no family in Australia and police are trying to contact her relatives overseas.

Twelve others were taken to hospital with stab wounds. One of them was Ms Good's nine-month-old baby, who was in a stable condition on Monday.