A Brisbane man who carried out a string of "terrible crimes", including fatally shooting a man he believed was committing domestic violence, has been jailed for 15 years.
Clayton David Backman, 31, was originally charged with the murder of Leslie Brooks in November 2016, but in the Supreme Court on Friday it was revealed he has already pleaded guilty to the lesser charge of manslaughter.
During a sentencing hearing in Brisbane, the court heard Mr Brooks was shot in the stomach at his former partner's Tingalpa home during an altercation with Backman, who was the woman's new partner.
The court heard it was accepted Backman had not intended to kill Mr Brooks and he had shot him in "self-defence using excessive force".
Crown Prosecutor Mark Green told the court some of the agreed facts, which alleged domestic violence committed by Mr Brooks, were not "the stated truth", but police had been aware of some reports.
However, Mr Green told the court these allegations were considered "the truth" for Backman.
"The crown therefore accepts they were believed by him and accurately represent his state of mind," he said.
The court heard Backman had been told by the woman that when her and Mr Brooks were together, he had repeatedly assaulted and raped her, and the violence had continued after their relationship ended.
On the day of the shooting, the court heard Backman had told police Mr Brooks had gone to the home, and he overheard him "barging in", before hearing the woman screaming "not in front of the children".
Backman, who had armed himself with a shotgun, said he confronted Mr Brooks, and the court heard Mr Brooks yelled at him: "You're not going to shoot me you weak c***."
The court heard Backman told police the pair went into the backyard, and Mr Brooks had "got so close he grabbed the gun", and then it was fired.
After the shooting, the court heard right before Backman handed himself in to police, he messaged his partner and said: "I really never meant for this to happen."
"But I can sleep OK knowing that you will always be safe now and those two beautiful kids will never have to witness his crap," the text message said.
'A mum's heart is not made for this kind of loss'
Mr Brooks mother, Carol Krezic read an emotional victim impact statement, telling the court "her whole world changed" the day her "loving son" died.
"I will grieve for the rest of my life," she said.
"It's the worst pain a person can go through... A mum's heart is not made for this kind of loss."
From the dock, where Backman was shackled at his wrists and ankles and armed by two correctional guards, he said to Mrs Krezic: "For what it's worth, I apologise."
Backman was also sentenced for more than a dozen other violent offences including a robbery a month earlier in October 2016, where he shot and injured a drug dealer.
The court heard at the time Backman had a serious drug addiction and a lengthy criminal history, including a previous assault of a woman and had spent much of his adult life in prison.
When handing down his sentence, Justice Paul Freeburn told the court his offending was "terrible" and had "tragic consequences".
"Not only for the victims but for their family and friends," he said.
Justice Freeburn told the court regardless of his reasons why, it was not acceptable to be armed with weapons.
"In a civilised society, in an Australian society, no normal human being carries around a loaded shot gun," he said.
Backman has already spent more than five years in custody, and must serve at least 80 per cent of his sentence.
