For the third time that night, Shane Raymond Bretag tried to separate "two idiots" at a Brisbane casino.
However, this time the former soldier used excessive force after experiencing hyper-vigilance and post-traumatic stress disorder as an Afghanistan veteran.
In a split second reaction, Bretag knocked unconscious a man who later required reconstructive surgery for extensive facial fractures.
CCTV cameras captured the moment the man was left lying bleeding on his back after an elbow to the face from Bretag in an August 2021 fight that started on a Treasury Casino escalator.
There was pre-existing animosity between Bretag's friend and another man who had clashed twice earlier that evening at the venue, Brisbane District Court heard on Friday.
Bretag had broken up the two confrontations.
Half an hour later they crossed paths again.
In "profoundly disturbing" CCTV footage, Bretag's friend and the other man throw punches at the top of a casino escalator before they wrestle near poker machines.
Bretag again tries to separate them as the other man's brother approaches.
Bretag quickly turns and hits the brother in the face with his elbow before turning to the brawling men.
When he realises the brother isn't moving, Bretag tries to help by placing him on his side in a recovery position before exiting as security approaches.
In a psychological report the court heard Bretag was hyper-vigilant to threats and suffered PTSD following his army stint in Afghanistan.
"It was that use of disproportionate force in a hyper-vigilant response to a perceived threat ...which places you in the dock today," Judge Ian Dearden told Bretag.
In a victim impact statement, the brother detailed the assault's physical and emotional toll.
He required permanent plates and screws in his face, and was forced to wear bands to limit his jaw movement for six weeks.
His recovery cost him more than $70,000 in estimated lost wages.
Judge Dearden said Bretag used force that was more than reasonably necessary while trying to defend his friend.
"Your motivation was trying to break up these two idiots who it seems had not been able tor resist having a go at each other throughout the night," he said.
"Had that elbow been somewhat lower and around the chest then you probably would have pushed him away."
Judge Dearden noted Bretag did try to help the brother before leaving.
"To your credit you went back to him. Leaving the premises is not flash ... but that was only after ensuring essentially that help was there (from security)," he said.
Judge Dearden also took aim at the brawling men after watching the CCTV footage.
"If they were children ... they would have been placed on detention and sent to the opposite ends of a very large school," he said.
"I hope that both the gentlemen involved who behaved like complete and utter idiots take some time to reflect on their role in the dispute that landed you in the situation you are in."
Bretag pleaded guilty to grievous bodily harm.
He was sentenced to two years in prison, suspended for two-and-a-half years.
Bretag was also ordered to pay $10,000 compensation.
