A man has been arrested by police in Melbourne over a fatal shooting in broad daylight at a Campbellfield shopping centre car park.

Officers from the Victoria Police Homicide Squad arrested a 27-year-old man from Greenvale, in Melbourne's north, today.

Key points: 27-year-old Greenvale man in custody

27-year-old Greenvale man in custody Man dies in hospital after being shot in Melbourne's Campbellfield

Man dies in hospital after being shot in Melbourne's Campbellfield Terrified shoppers sheltered inside shops during the ordeal

Police said a man was sitting in a car off Sydney Road in Campbellfield about 3:30pm on Monday when a gunman approached and fired several shots.

The victim, a 24-year-old Southbank man, was taken to Royal Melbourne Hospital with life-threatening injuries but died overnight.

No-one else was injured.

Terrified shoppers took shelter inside shops during the ordeal.

A witness, who did not want to be named, said a woman carrying a baby ran inside the shop and told staff there was a man with a gun.

"I heard four bangs. I thought it was construction work … it was pretty scary," she said.

"It was just surreal. You don't expect that in broad daylight [and] school holidays. It's just crazy to think that something could happen like that."

Another witness, who also did not want to be named, said he saw the victim lying in the gutter with bullet wounds to his legs and lower body.

Two men arrived and tried to help him before the ambulance arrived, the witness added.

Suspect seen fleeing in red Holden Commodore

The suspect fled the scene in a red Holden Commodore and was last seen heading towards the suburb of Dallas.

Investigators also received reports of a number of shots being fired into the air near the intersection of Riggall and Blair streets in Broadmeadows.

Police are appealing for information from people who may have witnessed the car park incident or who may have seen or heard shots fired into the air.

In a separate incident, a man who had been shot in the arm took himself to a hospital at Epping in Melbourne's north-east last night.

Police were also investigating reports of shots fired on Morey Street at Camberwell in Melbourne's east about 8:15pm. No-one was reported injured.