Details of murdered underworld figure revealed

New details about the life of murdered Melbourne underworld figure John Latorre have emerged as his links to the Calabrian mafia are uncovered.

There are fears of retaliation attacks following the execution style killing of Latorre, 64, at his Greenvale home yesterday.

Homicide detectives have claimed police have a mammoth task ahead of them as they attempt to work out who murdered Latorre.

READ MORE: Push for fresh inquest after man fatally injured trying to break up fight

The incident happened as Latorre, who ran a fruit and vegetable wholesale business at the Melbourne Market in Epping, planned to leave for work.

He had opened his garage door to go to his car when he was shot about 4.30am.

He was found by a family member with gunshot wounds to his upper body.

The 64 year-old is believed to have been a member of the Calabrian mafia.

"Police have a big battle ahead of them," former homicide detective Charlie Bezzina told 9News.

"It's a bit baffling as to why he may have been targeted. Is it internal or is it external? Only time will tell."

READ MORE: Police renew appeal after cyclist's shooting on Victorian trail

Latorre's brother, Vincent, was previously jailed for extortion activity and was named a suspect in the cold case murder of Rocco Iaria who went missing in 1991.

Iaria's body was discovered nearly seven years later near Shepparton.

In 2005, John donated to the Liberal Party as part of a suspected plot to get a visa for crime figure Francesco Madafferi, who is currently serving a jail sentence for one of the biggest ecstasy busts.

And the best man at his wedding was mafia figure Alfonso Muratore, who was also murdered in a gangland hit.

Latorre's fruit and vegetable wholesaler is a family affair, co-owned by John and his brother in law.

The business remained closed today, with relatives gathering at the family home to pay their respects.

There are now fears of possible revenge attacks leading to a new underworld war.