A "monster" who shot his son and his son's girlfriend at close range, pausing to reload between the killings as the young woman frantically called for help, has been jailed for at least 34 years.
Pawel Klosowski faced the South Australian Supreme Court on Thursday where Justice Anne Bampton said the "anguish and heart-wrenching pain" he had caused for the families involved was profound.
Fuelled by alcohol and enraged over an argument the 46-year-old's conduct became "irrational, reactive and ultimately violent", the judge said.
Klosowski had earlier pleaded guilty to the murders of his son Lukasz Klosowski and Chelsea Ireland, both aged 19, at his rural southeast property in August last year.
In recent submissions, the former truck driver admitted he could not explain his actions but thought about what he had done every day.
"I acted like a monster. The world would be a better place if I had shot myself instead," he said.
But prosecutor Kos Lesses said the apology was "too little, too late".
Mr Lesses said the shootings followed a row between Klosowski and his son after the teenager had indicated his intention to move out of his mother's house.
"The offending came about due to the insulting of the defendant's pride," the prosecutor said.
"And it was fuelled by the combination of two fatal causes, anger and alcohol."
Justice Brampton detailed how the argument had escalated with the killer berating his son at one stage for crying like a "little baby".
Acting deliberately and with purpose, Klosowski had retrieved the keys to his gun safe and loaded a shotgun before putting extra rounds in his pocket.
Lukasz was shot first in a bedroom and Klosowski had then reloaded his gun before firing at the locked bathroom door where Ms Ireland had hidden and called triple zero.
A second shot had killed her with her body found in the bath.
Because of his early guilty pleas, Klosowski was entitled to up to a 40 per cent discount on his minimum jail term. But Justice Bampton said such a discount would affect public confidence in the administration of justice.
The judge said the killings were at the higher end of the scale for murder offences.
"You were intoxicated, your pride was insulted and you became so enraged that you pursued your son upstairs," she said.
"Having shot and killed him, you pursued Chelsea and shot her dead."
The judge imposed the mandatory head sentence of life in jail and set a non-parole-period of 34 years, meaning Klosowski will be 80 before eligible for release.
Outside the court, Greg Ireland, the father of Chelsea said both families would "never understand how this happened".
"Today marks the end of one incredibly difficult chapter and tomorrow we continue the much more difficult task of learning to live without Chelsea and Lukasz," he said.
"They were just beautiful, beautiful kids.
"We've all got life sentences, but we're thinking this will probably be a life sentence for him as well."
The mother of Lukasz, Magda Pearce, said the teenagers were "so good together".
"We just want them back. They should be here," she said.