Shot Vic man's body not found for a week

Christopher Talbot and Luke Costin

A man may have lain dead inside a Melbourne house for more than a week before his body was discovered by neighbours.

The 49-year-old Deer Park man, who ran a sewing business from home, was found dead in his house on Erin Square on Monday afternoon, police said on Tuesday.

Investigations have revealed neighbours heard at least one gunshot about 3am on June 20 - a week before a neighbour and a person known to the man found his body.

Detectives believe the man hadn't been since June 15.

Police are yet to release details about where in the house he was gunned down or where the bullet or bullets hit his body.

Detective Inspector Tim Day says he's unsure how the killer got in and out of the house.

"I have no information to suggest there is a rogue gunman out there shooting at anybody," Det Insp Day told reporters.

"There will be a reason behind this, there is always a reason behind it.

"Whether the deceased is known to the offender, that's what the investigation will uncover."

The victim is believed to have been running a sewing or textile business from home and police are appealing to anyone who may have had business dealings with him to come forward.

Police are expected to remain on the scene for most of Tuesday.