The 46-year-old Mooroopna man was taken to hospital with life-threatening injuries after the alleged assault, but died on Monday, June 5.
The Homicide Squad is now investigating the incident.
Emergency services were called to a supermarket on McLennan Street about 7.15pm on May 22 following reports a man had been assaulted.
Matthew Atkinson, 19, of Shepparton, was previously charged by detectives in relation to the incident with intentionally causing serious injury in circumstances of gross violence, intentionally causing serious injury, recklessly causing serious injury, assault, assault by kicking, trafficking cannabis, possessing cannabis and dealing with property suspected of being the proceeds of crime.
The investigation will now be led by the Homicide Squad and the charges will be reviewed in due course.
A bail application for Mr Atkinson, which ended on Friday in Shepparton Magistrates’ Court with him being refused bail, heard that before the alleged assault, Mr Atkinson was yelling about an affair he believed the man to be in with an underage girl.
Shepparton Crime Investigation Unit’s Senior Constable Sarah Roberts said Mr Atkinson punched the victim to the head and body once, before he fell to the ground.
It is alleged Mr Atkinson then stomped on the man’s head twice, rendering him unconscious, before he fled the store.
Mr Atkinson remains in custody and will appear at Shepparton Magistrates’ Court in October.