Vic murdered man's brother missing

Police are still hunting the brother of a man viciously murdered at a major Melbourne shopping centre, one day on after the man's body was laid to rest.

David Dick, 36, died after being slashed in the head with a long-edged blade when he stepped out of a car park lift at Westfield Doncaster shopping centre on February 3.

His funeral was held on Friday, one week on from the attack.

Police say a person of interest in the investigation Mr Dick's brother Jonathan Dick, 39, who has been missing since February 6.

He was captured on CCTV footage near the scene of the crime on the day of the attack and the previous day.

He was recently diagnosed with a mental health condition and hasn't been taking his medication, police say.

Investigators say he might have travelled up to NSW where he has family or Queensland where his father recently died.

Police still don't know what motivated the attack.