Westfield Bondi Junction stabbing hero tells how he desperately tried to save an injured baby's life after infant and mum were attacked

A 'hero' who rushed to help a mother and nine-month-old baby after they were stabbed by a knifeman at Westfield Bondi Junction has told how he desperately worked to keep the infant alive. 

A major incident unfolded at the major shopping centre in Sydney's eastern suburbs about 3.30pm on Saturday afternoon after a knifeman went on a rampage, stabbing multiple people and killing at least four. 

Witnesses said the dark-haired man, wearing a Kangaroos NRL top, slashed and chased shoppers before he was shot by a female police officer. 

It is understood the baby is undergoing surgery and the mother is in a critical condition in hospital. 

A witness interrupted a Nine News reporter performing a live cross in Bondi Junction and pointed to his brother, saying: 'He's a hero - he saved the baby'. 

The clearly shaken hero said: 'The baby got stabbed and, yeah, the mum got stabbed. 

'The mum came over with the baby and threw it at me. I just helped by holding the baby ... and trying to compress the baby.'

He stood with the mother, tried to compress the blood using clothes from a store and called emergency services.  

'(It was) very bad... a lot of the blood on the floor ... hope the baby's alright,' the other brother said.

The mother had blood coming out of her mouth, he said. 

Another witness, a worker at the shopping centre, recalled seeing a mother screaming on the level above.

'I see a mother and maybe her partner with a baby in a pram,' she told Nine News.

'She's screaming really, really loudly. She's running back and forth not knowing what to do.

'Then she comes back to the pram and picks up her baby and there's just blood all over her back.

'The scream was unforgettable, it was the scariest thing I've ever seen.

'My co-worker took me, we locked all the doors, had to turn off all the lights and doors'.