A 10-year-old girl, a man, 25, and a woman, 32, died at the scene in Bourke St, while a fourth victim, a 33-year-old man, died in hospital on Friday night.
A three-month old baby is in a critical condition, a two-year-old is in a serious condition and a nine-year-old is in a stable condition at the Royal Children's Hospital.
Five patients at St Vincent's Hospital remain in a stable condition.
Deputy Commissioner Andrew Crisp told the Nine Network on Saturday police hoped to interview the accused man on Saturday, as he recovers in hospital from a non- life-threatening gunshot injury to his arm.
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"We're hoping that we can interview and charge him later today," he said.
Overall around 20 people were injured, while numerous people remain in a critical condition in hospital after pedestrians were mowed down on Melbourne's Bourke St mall.
It was the end to the 12 hour rampage after he allegedly stabbed his brother Angelo in the morning then evaded police for hours.
He was seen doing burnouts outside Flinders St Station before ramming the car into pedestrians walking in the mall.
Mr Crisp said a police inquiry will consider the fact the accused man was on bail at the time.
"We'll be looking at that as part of this investigation," he told the Nine Network.
"Generally our members are frustrated at times when people are given bail and there's subsequent offending.
"I think I want to actually focus on some of the positives. We saw the best of people yesterday. The support they gave to people on the street, it was amazing."
Swanston Street and the Bourke Street Mall are open, but the CBD remains closed off between Elizabeth and William Street, along Bourke Street.
Mr Crisp encouraged people to avoid the CBD.
"If you don't need to come into the city, if you don't need to come into that area, please stay away from the city."
Premier Daniel Andrews, Chief Commissioner Graham Ashton and Lord Mayor Robert Doyle will address the media at 10am.
