Haig Arslanian's fatal shooting of his younger brother David was a reasonable act of self-defence, a judge has found.
He was older than his 31-year-old brother, but he was significantly smaller and afraid of the man he shot and killed.
A Victorian Supreme Court jury found him not guilty of murder in July and on Thursday Justice Rita Incerti found him not guilty of manslaughter after a separate judge-alone trial.
The brothers' parents were in court for the verdict. Their father wept as another supporter gave a single clap and said: "He's free to go."
Another brother was also in court.
David Arslanian was shot and killed at the Geelong family home he shared with Haig and their parents in October 2020.
Haig Arslanian, then 39, admitted he was to blame for his brother's death and that he fired the gun that ended David's life.
Justice Incerti found prosecutors had not proven beyond reasonable doubt that Haig did not believe firing the shots at David was necessary in self-defence or that his response was an unreasonable one.
In a summary of her reasons, the judge said she considered her verdict weighing a background of family violence, Haig's significant mental health issues and a serious assault by David a month earlier.
She found that on October 5, 2020, the brothers were involved in an altercation which culminated in David smashing Haig's head into a mirror.
Almost immediately afterwards, Haig went to his bedroom and brought back a shotgun he had earlier taken from his father's gun safe.
"It was when David came toward or was lunging at Haig that Haig shot him twice in succession," Justice Incerti said.
She noted the physical disparity between the brothers, the history of violence and the threat David posed as he lunged toward Haig as well as Haig's perception there was no possibility of escape.
In the earlier trial, jurors were told there was frustration, anger and resentment between the men, who were no strangers to arguments and fights.
Haig believed David was using hard drugs and gambling, and understood he had stolen money from him and other family members.
In September, weeks before the shooting, Haig believed he was going to die when David tried to strangle him, his lawyer said.
At 190cm tall and about 170kg, David was substantially bigger than Haig.
He told police after the shooting that he hadn't intended to shoot David but just to scare him off.
Haig Arslanian is expected to walk free later on Thursday.
