Zachary Bryant, just three months old, was the youngest victim of a crazed driver in Melbourne on Friday (Jan 20).

Zachary's sister, two-year-old Zara, was also injured, but survived and is now in a stable condition.

Their parents, Matthew and Nawwar, issued a statement to the Australian media which described Zachary as "the most beautiful, loving, happy, and perfect little baby".

"He leaves us with the best three months and 14 days of wonderful memories spent in this world," the Bryants said. Mrs Bryant is from Kuala Lumpur, according to her Facebook page.

Zachary was reportedly thrown from his pram as the 26-year-old suspect Dimitrious Gargasoulas rammed his car into pedestrians along Bourke Street Mall, Melbourne's busiest shopping strip, last week.

The baby was so severely injured that he was rushed to the hospital in a police patrol car, as there was no time to wait for another ambulance to arrive, The Age reported.

He died on Saturday night.

Gargasoulas's car apparently hit 37 people, and four others were killed, including another child, 10-year-old Thalia Hakin.

The other victims were Mr Matthew Si, Ms Jess Mudie, and a Japanese national in his 20s.

Ms Mudie, 22, lived in Sydney and was visiting her older brother and his fiancee in Melbourne when she was hit.

Her family described her as the "most badass" daughter and sister in a statement.

Mr Si, 33, and his wife had just had lunch together and were returning to their offices when he was hit.

His wife Melinda said he was a devoted husband and loving father.

Fifteen people remain in hospital, with two still in critical condition, AFP said.

Mourners gathered at Melbourne's Federation Square for a minute's silence to remember those killed in the tragedy.

Gargasoulas has been charged with five counts of murder, Australian police said.

He failed to appear in court on Monday because he was unwell, his lawyer told Fairfax media.