Police say the victim was shot in the leg while he was in the car park of an Officeworks store on Sydney Road in Campbellfield just after 3.30pm on Monday.

An ambulance took him to the Royal Melbourne Hospital, where he later died.

"Police have been told a man armed with a firearm approached the victim in the car park, before shooting him a number of times in the leg," a police spokeswoman said.

"The offender then fled in what is believed to be a red Holden Commodore and was seen heading towards the Dallas area."

Investigators were also told that shots were fired a short time later in Broadmeadows, at the intersection of Riggall and Blair streets.

While the circumstances of that incident are still being investigated, police said they believe "a number of shots were fired into the air and a car matching the same description was also seen in the area".

No one else was injured.

Anyone who may have witnessed the shooting is urged to contact Crime Stoppers on 1800 333 000.