A gun believed to have been used in a police shooting possibly linked to Melbourne's criminal underworld has been found.

Police believe the weapon was used to shoot a 31-year-old policeman in the back of the head as he and his partner tried to pull over a car in Moonee Ponds last week.

Only 10 minutes earlier, gunshots were fired into the Broadmeadows home of George Williams, father of slain gangland figure Carl Williams.

The gun was found in Coburg near the intersection of Lyking and Sussex Streets, close to a burnt out four-wheel drive that is also believed to have been used in the attack, Detective Superintendent Peter De Santo said.

"It's a unique firearm, we do believe it is linked to the shooting and we do believe that somebody in the community will recognise it," he said.

Officers have also released security camera footage showing two men leaving the area where the vehicle was torched.

The car believed to have been involved in the shooting was found burnt out nearby at Coburg. ( ABC News )

Police would not rule out a link between last week's shooting and the fire bombing of a house in Essendon about 3:00am on Tuesday.

A number of the small explosives were hurled at a house on Albion Street, near where Carl Williams' wife Roberta lives.

"We are pursuing all avenues of investigations around the incidents around Essendon and north Coburg," Det Supt De Santo said.

Chief Commissioner Graeme Ashton last week rejected suggestions Melbourne's deadly gangland war was flaring up again.

"We've got a better understanding of that now and it's certainly true that we don't think at this stage that this is anything like what developed there 10 years ago," he said.

Police are appealing for anyone with information about the incident to contact them.