A drunk Victorian man attempted to murder a man who was probably already dead, thinking he was putting the man out of his misery.

Daniel James Darrington and Rocky Matskassy were fighting over a gun in March last year when the weapon discharged, its shot likely killing Mr Matskassy.

Mr Matskassy, 31, was lying bloodied on the floor when Darrington shot him again, believing he was still alive, the Victorian Supreme Court was told on Wednesday.

Darrington had seen Mr Matskassy's body twitch after the initial gunshot and wanted to put him out of his misery, defence barrister John Desmond told the court.

He was drunk, in shock, and believed Mr Matskassy was "all but fatally wounded".

"He makes the extremely poor decision to fire off the second shot," Mr Desmond told Darrington's plea hearing.

Justice Paul Coghlan said it was an irrational response.

Darrington, 39, intended to kill Mr Matskassy and believed he was alive at the time he shot him, he said.

He could have called triple zero or taken Mr Matskassy to hospital and they wouldn't be in the position they were, Justice Coghlan said.

The court heard Darrington assaulted Mr Matskassy after the pair argued at an associate's Melton South home on March 21.

Mr Desmond said it was Mr Matskassy who then produced the gun.

Justice Coghlan said he might not be able to rule on where the weapon had come from.

A jury in October found Darrington not guilty of murder, but guilty of attempted murder.

Crown prosecutor Peter Rose QC said Darrington should receive a significant sentence as he clearly intended to kill Mr Matskassy at the time he fired the second shot.

Mercedesz Matskassy said her little brother's death had been a devastating shock.

"He was my only sibling and last surviving member of my immediate family," she said.

Justice Coghlan will sentence Darrington early next year.

All parties involved in the case said it was very unusual and they couldn't find any similar ones for comparison.