Dimitrious 'Jimmy' Gargasoulas has been charged with five counts of murder after allegedly driving his car into crowds in Melbourne's Bourke Street pedestrian mall on Friday.
Five people died at the scene and in hospital after the rampage: Thalia Hakin, 10; Jess Mudie, 22; Matthew Si, 33; a three-month-old baby and a 25-year-old man.
Gargasoulas, 26, was taken into police custody after being released from hospital around 12:30pm on Monday (local time).
He refused to appear in court before a judge and it's expected he will return to court in August.
There are fears the death toll could grow with 15 people still in hospital, two with critical injuries.
As police waited for clearance from doctors to interview Gargasoulas, two of the victims' families remembered their loved ones taken during Friday's daylight attack.
Jess Mudie, 22, and Matthew Si, 33, were also among the dead. Mr Si's family said they were "shattered" by what happened.
His wife Melinda had just had lunch with him when he was hit by the car; she described him as a devoted husband, father, brother and son.
"The family would like to thank everyone who helped Matt at the scene and did their best to save him," she said.
Meanwhile, in a letter released on Sunday, Ms Mudie's family described her as a "bright bubble of joy" with a great sense of humour.
"We are constantly inspired by your love for everyone around you and the lengths you will go to for the people you love.
"You are strong, beautiful, determined, always work hard to get what you want and never shy away from a challenge."
A memorial service for 10-year-old Thalia Hakin was held on Sunday night. Her nine-year-old sister Maggie and mother Nathalie were caught up in the crush of pedestrians trying to flee the scene; the latter is in intensive care.
In response to Friday's rampage, Victoria Premier Daniel Andrews on Monday announced a new Night Court. It means magistrates would be available at night and on weekends to consider bail applications for those charged with violent offences where police oppose bail.
A former Supreme Court judge has also been asked for urgent advice on other possible changes.
Gargasoulas' mother Emily has disowned her son, saying she no longer wanted to be associated with him.
"I feel so ashamed and bad, you know," she said. "I don't want to be known that I'm the mother."
She went on to add she wished he would "go to Hell and die in Hell."
Ms Gargasoulas said she saw the bloodied fight between Gargasoulas and his brother Angelo, which happened before the rampage.
Angelo was stabbed in the face in the fight - reportedly sparked by his sexuality - and Gargasoulas's pregnant partner was allegedly taken hostage.
In his car, Gargasoulas began doing burnouts near the busy Flinders St station, where he was seen in the background of a television live cross.
From there, he sped along Swanson St and then into the Bourke St mall sending pedestrians scattering for their lives.
A makeshift memorial has sprung up at the corner of Elizabeth St and Bourke St Mall, with flowers and emotional messages being left.
It has been visited by Prime Minister Malcolm Turnbull, Labor leader Bill Shorten, Lord Mayor Robert Doyle and Mr Andrews.
The Victorian government has also set up the Bourke Street Fund, making the first donation of $100,000 to help the families of those killed on Friday.
"Victorians showed remarkable courage, and came to the aid of family, friend, and stranger. And as we heal, Victorians can continue to help those who have been most affected," the government says.
The government says the fund will work with other services and offer support to those injured or who witnessed the attack.