Two drug dealers begged for their lives as the toolbox they were locked in was dumped into a lagoon south of Brisbane, a court has heard.
The decomposed bodies of Cory Breton, 28, and Iuliana Triscaru, 31, were found in the metal box in the water in February 2016.
Stou Daniels and Davy Malu Junior Taiao, both 26, Trent Michael Thrupp, 27, and Waylon Ngaketo Cowan Walker, 31, are accused of murdering the pair at Kingston in Logan 18 days earlier.
Mr Breton's friend Lelan Harrington told the Brisbane Supreme Court on Thursday he was in a unit with the pair on January 24, but didn't accompany those who allegedly disposed of the toolbox.
Mr Harrington said he asked Thrupp about Mr Breton and Ms Triscaru's final moments as the box was put into the Scrubby Creek lagoon on January 24.
"He told me they were begging for their lives and that he shot them both in the head," Mr Harrington said.
He also told the court Thrupp said tyres and rocks were used to sink the toolbox and holes put in because it kept floating.
Mr Harrington said he was charged with deprivation of liberty and assault occasioning bodily harm over his involvement, but avoided spending time in jail.
Under cross-examination, he admitted heavy drug use before the killings and numerous dealings with police.
Mr Breton and Ms Triscaru were summoned separately to the Kingston unit because alleged dealer Daniels was suspicious Mr Breton was "a dog" or informant, Mr Harrington told the court.
He said Mr Breton and Ms Triscaru's wrists and ankles were bound with zip ties and duct tape, and kept in the unit for hours.
They were put in a toolbox brought into the lounge room, but when Mr Harrington saw Ms Triscaru near a sliding door, he panicked and alerted the other men to her "getting away".
Afterwards Mr Harrington said he saw Ms Triscaru on the ground with blood coming from her mouth.
He told the court one man put his hands on her mouth to stop her screaming before another put a zip tie around her neck.
Later Daniels "started slicing her forearms" when Ms Triscaru tried to stop him shutting the toolbox lid with the pair inside, Mr Harrington said.
He said the group drank bourbon, smoked ice and played loud music and electronic games while Mr Breton and Ms Triscaru were kept captive.
Sheets and towels used to clean up blood were put into garbage bags and placed inside the metal box with the two dealers.
When the toolbox was put onto a ute the pair could be heard "kicking and screaming" inside, Mr Harrington said.
Police divers found the bodies of Mr Breton and Ms Triscaru inside the toolbox in the lagoon.
They died from either asphyxiation or drowning.
All four men pleaded not guilty at the start of the trial to two counts of murder, while Daniels, Taiao and Thrupp also denied torturing Mr Breton and Ms Triscaru.
Thrupp pleaded guilty to the pair's manslaughter, but that plea wasn't accepted by the Crown.
The trial continues.
Australian Associated Press