A first-time mother was among those killed in a shock stabbing spree at a Sydney shopping mall, with her nine-month-old baby undergoing surgery after suffering knife wounds.

Six people were murdered at the Westfield Bondi Junction centre on Saturday afternoon, with the attacker shot dead by a “heroic” off-duty female police officer who had responded to the scene.

Ash Good, 38, is the first victim to be identified, with witnesses reporting that she handed over her small child to other terrified shoppers for them to carry out make-shift medical aid.

Two brothers said they tried to help her and her child using shirts from the shop they were sheltering in to stop the bleeding.

One of the brothers told 9News Sydney: “We were just shopping and saw the man run up to the woman with the baby and then we were both ready to go and help out.

“But I just said to my brother, ‘We’ve got to run in’ – [we] ran in, told the guys to lock up the doors and then the mother came with the baby bleeding, stabbed and we got them into the store and just got them safe and then rang for help.”

He added that his brother “helped with holding the baby, and trying to compress the baby, and [the] same with the mother – trying to compress the blood from stopping, and call the ambulance and the police.”

She was later confirmed as one of the deceased victims, with New South Wales police commissioner Karen Webb telling reporters it was “too soon” to provide an update on her child’s condition.

In the first tributes from those who knew her, Ms Good was described as a “beautiful person, a wonderful athlete”, who had been “so excited” to welcome her child.

Local media has reported that, just hours before the stabbing spree, Ms Good posted a video on Instagram of her daughter in her car seat, eating a snack, to the soundtrack of My Girl by The Temptations.

Emergency services were contacted at around 3.30pm local time after a lone knifeman entered the mall and began indiscriminately attacking shoppers.

A shocking video shared online appears to show a shopper confronting the attacker, who is wielding a large blade, on an escalator by holding a bollard towards him.

Four women and a man died within the shopping centre, while another woman, believed to be Ms Good, was confirmed dead after being rushed to hospital. Eight people, including her child, are in hospitals around Sydney receiving treatment for “different injuries”.

A female New South Wales Police inspector has been hailed a hero after she confronted the attacker on her own, shooting him dead as he raised a knife and lunged at her.

At a press conference, Anthony Cooke, the force’s assistant commissioner, said: “This all happened very, very quickly – the officer that was in the vicinity attended on her own, [and] was guided to the location of the offender by people who were in the centre.

“She took the actions that she did saving a range of people’s lives; (she was) an inspector, a senior police officer – she was on her own.”

Police have said they believe the attacker was a 40-year-old male who was previously known to law enforcement agencies. While no motive has yet been established, it is not believed to be a terror-related incident.

A supervisor of a luggage store in the centre said he witnessed the attacker stab a woman and saw the bodies of four people on the ground, including two security guards.

Yohan Francois Philip, 29, said a woman fleeing the attacker ran to his shop, “banged on the door and said let me in”.

He added: “As I was letting her in, the perpetrator fell behind her with a knife and I saw him and so did the other customers in the store locked in with us and so we quickly pulled her in, [and] locked the door. He got up and we realised he [had] just stabbed two security guards.

“Then he ran across to the corner part of the luggage store, to the premium section, and he stabbed a woman, which I saw happen right in front of me.”

Another shopper also described the attacker heading in her direction before the female officer shot him dead.

“If she didn’t shoot him, he would have kept going,” she said. “He was on the rampage.

“Then she walked over and gave him CPR. He had a big blade on him – she chucked the knife away. He looked like he was on a killing spree.”

King Charles said he and the Queen were “utterly shocked and horrified” by the “senseless attack” in Sydney and their “hearts go out to the families and loved ones of those who have been so brutally killed”.

Prince William and Kate also offered their condolences, saying they were “shocked and saddened by the terrible events”.