It was likened to a scene from the Wild West.
Armed with a sawn-off rifle with one bullet, Justin John Meale was in a stand-off with Clinton "Rocky" Pollock on Father's Day 2018 after a drug deal went bad.
Fearing Mr Pollock had a semi-automatic weapon and would get "sprayed", Meale thought he better shoot first.
"I don't know if you have ever watched that American series Justified - (it's like) who drew first?," defence barrister Greg McGuire earlier told a Brisbane Supreme Court jury.
"It is almost like something from the Wild West".
Meale thought Mr Pollock looked "sketchy" with a hand in his pocket when he approached.
Then Mr Pollock "twitched" during their stand-off, Meale said.
"I was scared thinking I have pretty much taken a knife to a gun fight with a single shot .22," Meale later told police.
"I was thinking 'alright I've just got one shot, if he is going to shoot me, I will shoot him first'.
"I have just gone bang. That was it. It was that quick."
Mr Pollock, 35, was shot in the torso outside his Deception Bay house north of Brisbane and died soon afterwards.
Police did not find a weapon at Mr Pollock's home.
Crown prosecutor Danny Boyle said Meale was always going to shoot Mr Pollock after travelling to his house and luring him out to the front gate.
"There was going to be a conflict, and he (Meale) knew it," Mr Boyle told the court.
The pair had fallen out after Mr Pollock did not receive drugs from Meale in exchange for a bag of bullets in a deal organised the previous day.
They had traded text messages with increasing hostility.
"I will spray your whole house up," Mr Pollock said in a text to Meale read to the court.
"If you don't want me to come there and play up, that little toy you have got is not going to stop me, let me tell you.
"You've got one bullet in the chamber. I have got 15 so don't go mouthing off to me you goose."
Meale made the "unbelievably stupid decision" to travel to Mr Pollock's house with three others to teach him a lesson.
"Stupidity is not a criminal offence," Mr McGuire told the jury.
Mr Pollock was described as "no angel" and "someone you didn't want to piss off".
However, his mother Donna's victim impact statement detailed how much he had been missed, with his daughter saying how she wished her dad had not missed her formal.
The jury in the one-week trial found Meale guilty of murder after starting their deliberations earlier on Tuesday.
The court heard Meale suffered significant behavioural and developmental issues as a child, diagnosed with Asperger's syndrome and autism spectrum disorder.
Meale descended into drug abuse after dropping out of year eight and had a criminal history by the age of 17.
He was sentenced to a drug-related offence by 21 and had also received convictions for domestic violence order breaches.
Meale on Tuesday received a life sentence from Justice Thomas Bradley with 1541 days in custody declared time served.
