The driver accused of mowing down pedestrians in Melbourne's CBD is expected to face a murder charge following the death of an 83-year-old grandfather.

Antonios Crocaris, 83, died in hospital at about 11.30pm yesterday, eight days after becoming one of 18 people hit by a car that drove down tram tracks in Flinders Street and into pedestrians.

Six of those injured remain in hospital.

In a statement, Mr Crocaris' devastated family called him "Our Dad, our hero."

"Our father Anton had his life cruelly taken away in a senseless act of violence," they wrote.

Antonios Crocaris's family said he is "irreplaceable". (Victoria Police)

Saeed Noori has been charged over the incident. (Supplied)

"These circumstances are devastating to our family. Dad is simply irreplaceable and we will never fully recover from this loss.

"He was a beloved husband of Elizabeth, adored father of Freda, Tony and Bill, and cherished grandfather of Verity, Lysander and Jackson."

Mr Crocaris' family said he was a "friend to all and proud citizen of Australia".

"Our deepest gratitude to the wonderful people of Melbourne and dedicated first responders who rendered him and others every assistance. Special mention to the caring staff of The Alfred Intensive Care Unit."

Mr Crocaris is the first fatality from the December 21 attack.

Six people remain in hospital. (Supplied)

Nineteen people were injured when the car ploughed through a pedestrian crossing. (AAP)

"This is such a shocking, tragic, needless loss of life," Assistant Commissioner Doug Fryer told reporters today.

Acting opposition leader Tanya Plibersek said she and all Australians were thinking of Mr Crocaris' family.

"Our thoughts are with the man's family and friends and the families and friends of all of those injured.

"This has been, obviously, a very distressing time and I'm sure that all Australians send out their thought, their love, their prayers," she told reporters in Sydney.

Australian citizen and Afghan refugee Saeed Noori, 32, was arrested following the attack and charged with 18 counts of attempted murder and one count of conduct endangering life.

One of those charges is expected to be upgraded to murder.