It was a poignant illustration of the void left by the Comanchero outlaw motorcycle gang's Canberra commander, whose family members groaned, recoiled in horror and wiped away tears as they watched confronting CCTV footage of his death at Civic nightclub Kokomo's.

This all preceded the self-described coward who killed him, Frederick Elijah Mercy Tuifua, 27, being sentenced in the ACT Supreme Court to 20 years in jail.

Justice Michael Elkaim, after describing the murder as incomprehensible, imposed a non-parole period of 10 years.

Tuifua, a former Canberra Grammar School student, pleaded guilty in April to charges of murdering Mr Ulavalu and intentionally inflicting grievous bodily harm on another bikie, Zachary Robb, during a July 2020 brawl at Kokomo's.

He also pleaded guilty on Friday to an assault occasioning actual bodily harm charge, laid over his role in a five-on-one bashing in Canberra's jail last November.

The nature of the case had authorities on high alert, with a large police presence outside the courthouse and sheriff's officers ensuring the respective families of Mr Ulavalu and Tuifua sat, separated by detectives and journalists, on opposite sides of the courtroom.

Those in the public gallery were forewarned about the graphic nature of the Kokomo's surveillance footage that was shown when the sentence hearing began, and some people who knew Mr Ulavalu went outside when it all became too much.

They had just seen Tuifua standing back as a brawl erupted, and eventually inserting himself into the melee by plunging a military-style knife into Mr Ulavalu's neck from behind as the victim tried to break up the fight.

The killer then stabbed Mr Robb, who was being restrained by three men, in the thigh, before fleeing the nightclub and sending a security barrier crashing to the ground outside.

A mortally wounded Mr Ulavalu staggered into the street after his assailant, leaving a trail of blood in his wake, and nearly tripped over the barrier before collapsing in a gutter.

Mr Ulavalu's partner, Monique Eramo, was woken a short time later by what she told the court on Friday was a devastating phone call that still haunted her.

Ms Eramo was 14 weeks pregnant at the time with a child she said Mr Ulavalu was thrilled about, but one whose gender the 48-year-old victim did not live long enough to learn.

"We had our first Father's Day and, unfairly, all my child had was a portrait of her dad," she said through tears.

"That is all there will ever be: photos, videos and distant memories."

Ms Eramo described Mr Ulavalu as someone who had "a genuine and infectious presence", and who would "always be remembered for his greatness".

Tuifua sat behind large panels of glass rather than in the dock throughout Friday's proceedings, when he entered the witness box at one stage to give evidence.

His partner has also given birth to a girl since the murder, and the softly spoken man said he was "sorry from the bottom of my heart" for his actions.

"I watched the [CCTV] and I don't even know who that person is," Tuifua said.

"I had a life, and I thrown it all away in that moment."

The murderer said he had routinely carried a knife for "protection", but he struggled to explain why he had used one to attack two men who could not defend themselves.

"I'm a coward," he said.

Tuifua's barrister, Bret Walker SC, told the court his client's remorse was sincere.

He described the killing as a tragic event that had no logical explanation, with the "trivial" issue of a missing bag that belonged to one of the killer's associates having seemingly prompted the brawl.

"We do say, of this offending, it's entirely bereft of hatched plans and fostered hostilities," Mr Walker said.

Crown prosecutor Anthony Williamson said Justice Elkaim might find the apparent lack of a motive "quite disturbing".

"Without any warning and without any explanation, [Tuifua] has killed another human being," he said. "We do not know why."

Mr Williamson, like Tuifua himself, described the Kokomo's offending as "cowardly" and noted its very public nature, saying 116 patrons were in the nightclub at the time.

Justice Elkaim later mentioned this as well, referring to the many "innocent bystanders".

"The public was exposed to the horrors of seeing a man dying in the gutter of a public street," he said.

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The judge also highlighted the impact of the episode on Mr Ulavalu's family, saying the victim's status as a gang leader was "not relevant".

Of the murder itself, Justice Elkaim said the CCTV footage revealed Tuifua "seemed intent on using the knife by having it in his hand for some time before the stabbing".

He was left with little doubt Tuifua was "an aggressor that night".

The judge ultimately accepted, however, that the 27-year-old's actions had been out of character, that he had shown genuine remorse and that he had good prospects for rehabilitation.

While he backdated Tuifua's sentence to the date of his arrest in August 2020, the non-parole period only begins a year later and the killer will therefore spend a minimum of 11 years in custody before becoming eligible for release in 2031.

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