UPDATED 4.34PM The fourth person to die after being struck by the car which was driven into crowds in Melbourne's CBD yesterday was a young dad on his lunch break, it has been revealed. 

The man, aged in his 30s, died from his injuries in hospital last night. 

He was on his lunch break when he was hit by a car driven by 26-year-old James 'Jimmy' Gargasoulas and leaves behind a wife and baby boy, Ten News reported. 

 Three other people - including a 10-year-old girl - died at the scene. The two other victims were believed to have been a man and woman - both in their 30s.

Up to 31 people were injured in the tragedy which unfolded on Bourke St and police fear the death toll could climb even higher. 

Victorian chief police Commissioner Graham Ashton told the Herald Sun police had grave fears for "two or three" of the people who were badly injured in the rampage. 

Twenty four people remain in Melbourne hospitals. Seven of the injured - including a 3-month-old baby - are in a critical condition and at least another six have serious injuries. A two-year-old was among those seriously hurt. 

READ MORE: Melbourne carnage not terror related

At least four other people who were hospitalised after the carnage have now been discharged.

The Royal Melbourne Hospital​​'s director of emergency medicine has praised the dedication of medical staff treating injured victims after the incident, which he called a "senseless" loss of life. 

Eleven people, including three in a critical condition, were rushed to the hospital's emergency department in less than an hour-and-a-half - between 2.16pm and 3.30pm yesterday. 

Professor George Braitberg, who heads the busy emergency department,  told The Age he was flooded with so many doctors and nurses wanting to help the patients, that he had to start turning them away.

"Watching it with trained eyes, although it was really busy and looked chaotic, it was absolutely beautifully performed. It was almost like an orchestra," he said. 

"You work on that adrenaline. Your energy is so focused and you have so much adrenaline that there has to be a deflation afterwards. So, once it was all over, we've had what we call a 'hot debrief' so everybody could talk about it."

Braitberg​ said he was at the hospital this morning speaking with staff who had treated victims of the incident. 

"You start to think about the human loss, and the senseless human loss that occurred, and that's partly because we get more information and partly because all that adrenaline is gone," he told The Age. 

Bourke St has now reopened to the public and a memorial has been set up at the mall, where members of the public are laying flowers and tributes to those killed. 

Australia's bail laws will be reviewed in the wake of the tragedy, the Herald Sun reported.​

The man accused of driving into the crowed in a stolen red Holden was granted bail last weekend for family violence charges. 

Police had opposed the request for Gargasoulas to be bailed, but a bail justice decided to him release him. 

Today, Victoria Premier Daniel Andrews said bail would be reviewed as part of investigations into the tragedy. 

"Let's deal with the facts of these things, let's properly understand what's gone on here, and then let's make, if necessary, a change that is fundamental to honouring the legacy and memory of those who have died."

"The events of yesterday, where we are standing, are a great tragedy for our state and our nation.

"They sadden us, they fill us with grief and anger and ti's an anger that is shared by every single decent Victorian. We want answers, we want someone to explain what has gone on.

"When we think about hundreds and hundreds of ordinary Victorians who came to the aid of complete strangers, who reached out in an act of care and compassion and instinctive act of protection, an instinctively Victorian and Australian reaction to the worst of circumstances." 

Chief police Commissioner Graham Ashton told the Herald Sun that police were often "frustrated" when judges granted offenders bail.

However, he said he respected the authority of the courts to make such decisions. 

Twitter users have echoed Ashton's sentiment, with one saying "courts are letting us down badly".

"Devestating that once again the Vic justice system has let the public down. #bourkestreet offender out on remand against police requests (sic)," another woman tweeted. 

The coroner would investigate how the police dealt with the tragedy, Ashton said. 

"All decisions our officers made were in the interests of trying to provide community safety, I'm absolutely confident of that. But as I say, these matters will be absolutely examined by the coroner, and we absolutely welcome those examinations."

Gargasoulas, who also goes by the first name Dimitrious, was shot in the arm by police and is now in hospital under police guard with non life-threatening injuries.

A relative said the Gargasoulas had a history of drug problems and had been in out of jail for car theft and drug offences, The Age reported.

He was charged over a family violence incident less than a week ago and was well-known to police.​