A single blow to the jaw was all it took to kill Queensland father Timothy Lang.
He fell back and hit his head on the concrete footpath outside of the Fox Hotel in South Brisbane after being punched by a jogger, and later died in hospital.
The man who hit Mr Lang and left him lying motionless on the ground, Wayne Andrew Hearn, has been sentenced to eight-and-a-half years behind bars for the 2016 attack.
Hearn had gone for a run on the morning of October 8 when he passed Mr Lang heading in the opposite direction on Melbourne Street, but turned back when he made a comment.
The pair knew each other and exchanged words before Hearn punched Mr Lang and began to walk away.
He returned seconds later and stood over his unconscious victim, saying words to the effect of "I told you to stop" and "that's what you get".
Hearn told onlookers to call for help and then left.
The Brisbane Supreme Court was on Tuesday told Mr Lang had previously pointed a gun at Hearn, and that his mention of the weapon that morning had provoked haunting memories for him.
As a boy, Hearn witnessed his father shoot his uncle in the head, was exposed to violence and alcohol abuse and lost close relatives in a car crash.
He also has an extensive criminal history that includes random acts of violence against complete strangers and people he knew intimately.
Justice Peter Applegarth said Mr Lang did not deserve to have his life cut short.
"You threw a punch which tragically took a life," he said.
"His verbal provocation did not excuse your reaction, you overreacted."
But Hearn's lawyer said his client hadn't meant for Mr Lang to die.
"He actually indicated that he was praying for the victim while the victim was still on life support, and hoping that he wouldn't die," Carl Martinovic said.
After the attack, Hearn told his then-girlfriend and his mother he'd hit Lang, and asked a former partner to call the hospital to check on his condition.
In a handwritten letter he read to the court, Hearn said he was sorry.
"I wish time could be wound back and that my behaviour was different," he said.
"However, time cannot be turned back and now both of our families are left with these tragic consequences."
Hearn, who had pleaded guilty to unlawful striking causing death, must serve 80 per cent of his sentence before he is eligible to apply for parole.
Australian Associated Press
