Two men had stormed the Deer Park home late on Saturday night, pulled out their guns, and shot the man multiple times in the leg while he tried to fight back during the two-on-one brawl.

He managed to stab one of the two men during the fight before the pair ran from the Winslow Crescent property and fled in a car, police said.

The shot man's partner was home at the time, but she was uninjured during the home invasion.

Detective Acting Sergeant Stephen Eppingstall called it a brazen attack on two unsuspecting people.

But he couldn't explain why the couple didn't call police for more than 10 hours after the shooting.

"We're not sure why it's taken so long to report it," he told reporters at the scene.

"I couldn't tell you, to be honest. It's a bit weird."

Paramedics were called to the home at 8.59am on Sunday, Ambulance Victoria spokesman John Mullen said.

The shot man was treated at the scene and taken to the Royal Melbourne Hospital in a stable condition.

One of the suspected attackers, a 32-year-old Hillside man, was dropped off at Sunshine Hospital about 1am on Sunday.

Mr Mullen said paramedics had transferred the man to the Royal Melbourne Hospital about 2.30am in a critical condition.

The man remains under police guard at the hospital while the second offender remains on the run.

Police are still trying to piece together how the men gained access to the home and where they had parked their getaway car.

It's possible the men had parked in a locked paddock behind the home.

A motive for the attack is unknown at this time, police said.

Anyone with any information can contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppersvic.com.au.