Carlo Piero Stewart, 31, died after being shot during a confrontation between two groups of men at Ipswich, west of Brisbane, on July 27, 2021.
Tye Joshua Bickle from Logan, Brayden Alan Wilson-Knight of North Booval and a boy who was aged 16 at the time were originally charged with murder.
The trio on Monday each pleaded guilty to manslaughter and two counts of grievous bodily harm.
Police alleged that around 5pm on the day of the shooting two groups arranged to meet on Baden Jones Way in the Ipswich suburb of North Booval in relation to a dispute over property.
A fight broke out between the group of nine males, some armed with baseball bats and one with a firearm.
Mr Stewart died at the Ipswich Hospital from two gunshot wounds.
Four others were also taken to hospital, including a 29-year-old Heritage Park man with critical head injuries.
All three defendants on Monday said they did not have anything to say as to why sentences should not be passed.
Justice Peter Callaghan sought a "full account" from the prosecutor and defence barristers for why there had been a sudden change in plea in a matter stretching back years.
"The court had a large block of time set aside to hear the trial of this matter," he said.
"I apprehend that the defendants will all make something of the delay and to the fact they have had a murder charge hanging over their head."
Accepting the pleas at a "late stage" would be relevant to sentencing as well as the natural interest of the court, Justice Callaghan said.
The three defendants are due to face sentencing on September 25.
Bail for all three men was continued.
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