Tony Panagiotou didn't tell his sons to calm down and go back to sleep after they woke him up in the middle of the night and told him about a plan to retrieve some audio equipment they thought had been stolen.
Instead, the 59-year-old grabbed a shotgun and drove off with his sons George, 22, and John, 18, to a south-east Melbourne home where DJ equipment they had rented out through their business was being advertised for sale on Gumtree for $3500.
Panagiotou on Friday faced Victoria's Supreme Court, where he was jailed for a total of nine years after pleading guilty to the manslaughter of Duane Hutchings, whom he shot once in the head at the Oakleigh East residence in February 2019.
Justice Lex Lasry described the killing as an act of "tragic stupidity".
"When woken up by your sons and told of their intention, instead of dissuading them you came with them and brought a firearm," Justice Lasry said.
"Your actions made the catastrophes inevitable."
Panagiotou and four others began assaulting Mr Hutchings after confirming the DJ equipment was inside.
The 59-year-old later told police he raised his gun when he thought he saw Mr Hutchings reaching for a weapon and that he didn't mean to pull the trigger.
The group fled after dismantling and packing up the DJ equipment.
"I took a man's life, I'm not a good person. Look what I've done," Panagiotou told police.
His lawyer Malcolm Thomas said Panagiotou had experienced absolute shame and self loathing since the killing.
He said he experienced hyper-vigilance and obtained the weapon after a home invasion in 2006 which had a lasting impact on his mental health. He just wanted to protect his children.
Police had already told them not to go, after attempts were made to report the equipment stolen. Officers told them they couldn't follow it up because it was a civil matter.
"This was most unfortunate given what was to come," Justice Lasry said on Friday.
Panagiotou was originally charged with murder and had been set to stand trial before he pleaded guilty to manslaughter in October.
"For almost three years I have wondered about the man who shot my nephew in the back of the head," Mr Hutchings' aunt Tina told the court.
"Those words are shocking and its still a shock to me that I have to say them."
Panagiotou must serve at least six years behind bars before being eligible for parole.
