A dedicated detective is now fighting for his life after he was stabbed in the chest by a child rapist in the middle of a packed Sydney pub celebrating Australia Day.

Detective Sergeant John Breda was stabbed in the chest and abdomen when he tried to arrest Nick Newman, 33, at about 3.10pm at Maroubra Junction Hotel on Anzac Parade.

The 45-year-old senior detective, once awarded with a National Medal in 2015 by the Prime Minister, was rushed to St Vincent's Hospital in a critical condition, and will undergo emergency surgery as doctors battle to save his life.

Assistant Commissioner Mark Walton said a lot of people were concerned about the senior officer as he is 'very well regarded'.

'We’re certainly very concerned about his condition and our thoughts are with him and his family,' he said.

Daily Mail Australia understands Newman, 33, cut his own throat with a knife before he was shot dead in the beer garden of the hotel by another two officers.

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A hero detective was stabbed and his child rapist attacker was shot dead at a pub in Sydney

Detective Sergeant John Breda, (pictured) was stabbed in the chest and abdomen when he tried to arrest Nick Newman, 33, for child sex offences

Wanted child sex offender Newman (pictured) stabbed the senior detective before he was shot dead at the scene by another officer

A dozen police cars and ambulances rushed to the scene on Anzac Parade, shutting down area

A man was seen being escorted from the scene in handcuffs by police shortly after incident

Bar staff were escorted from the building in Maroubra after the shooting on Friday (pictured)

Wanted for child sex offences, Newman, 33, reportedly failed to appear in court two days ago and police sent out a public appeal to find the man.

Newman was wanted for six counts of rape, one count of intentionally choking and one count of aggravated sexual assault against a person under 16, the Daily Telegraph reported.

The child sex offender stabbed the senior detective when the 45-year-old and his partner from the sex crime unit stormed the hotel to arrest Newman.

The 33-year-old reportedly began arguing with the detectives before he attacked with a knife, where Sgt Breda's two colleagues shot Newman.

Sgt Breda is a veteran of the Child Abuse and Sex Crime Squad and has spent time in the Middle Eastern Organised Crime Squad.

Dramatic video shot by a witness at the scene showed officers with guns draw at a back entrance to the pub, before entering in combat stance.

The officer was seen arriving at the hospital surrounded by concerned colleagues while paramedics worked on him.

The attacker was shot dead by officers on the scene with witnesses saying they heard four or five shots.

Two 18-year-old boys who heard the commotion told Daily Mail Australia it was 'pretty scary'.

'Our friends were inside and we heard the shots so we hurried to see what was going on. There was blood everywhere,' Mackenzie Gibbs said.

'Our friends were inside and we heard the shots so we hurried to see what was going on. There was blood everywhere,' Mackenzie Gibbs (left) told Daily Mail Australia

The senior officer was rushed to hospital for emergency surgery and is in a critical condition

NSW Police Assistant Commissioner Mark Walton (pictured) said the senior officer was stabbed in chest and abdomen

Another man was seen being marched away from the pub by police but it was not clear why he was arrested.

At least 20 police officers locked down the area, putting up tape and telling nearby businesses to close.

Sales assistant Lara Alexander was working at the nearby Pharmacy 4 Less when she heard 'four or five' gunshots.

'I was vacuuming here at work and I heard gunshots from a couple of doors away. About four or five,' she told Daily Mail Australia.

The officer was seen arriving at the hospital surrounded by concerned colleagues while paramedics worked on him

A large number of police officers were at the scene and were seen talking to people

At least 20 police officers locked down the area, putting up tape and telling nearby businesses to close

A witness told reporters: 'I reckon about four or five shots, easy... bang, bang, bang, bang, bang... we saw blood everywhere... it all just happened so suddenly.'

Noel Whelan has been staying at the Maroubra Junction Hotel for a few months and was shocked when he was ushered out and into the street this afternoon

'I went outside and there were three or four ambulances and a whole bunch of police cars.

'And then I saw someone on a stretcher come out of the pub and another guy in handcuffs.'

Another witness told reporters: 'I reckon about 4 or 5 shots, easy... bang, bang, bang, bang, bang... we saw blood everywhere... it all just happened so suddenly.'

Noel Whelan has been staying at the Maroubra Junction Hotel for a few months and was shocked when he was ushered out and into the street this afternoon.

Mr Whelan said he saw the police officer being brought outside and he 'didn't look very comfortable at all'.

Dramatic video shot by a witness at the scene showed officers with guns draw at a back entrance to the pub, before entering in combat stance

Large number of police congregate outside the Maroubra Junction Hotel

'I knew something was wrong when the police came pouring in. There were sirens coming from everywhere,' he told Daily Mail Australia.

'I heard what could have been a muffled gunshot but didn't think anything of it until I went down stairs and there were police everywhere.'

Mr Whelan stays in Maroubra for six months every year and is saddened by the incident.

'I just want to get back to Europe. I didn't expect anything like this to happen in Australia especially not in Australia Day.'

The homicide squad will now investigate all circumstances surrounding the incident, including the officers shooting the attacker, police said.

The investigation will be independently reviewed and a report prepared for the coroner.

'My thoughts and prayers are with the family and colleagues of the NSW Police officer injured in Maroubra this afternoon,' NSW Police Minister Troy Grant said.

'Thank you to the team at St Vincent's who are caring for him now.'