A former colleague of Beau Lamarre-Condon told a trial he told her he had "done something bad" after arriving at her home.
She said the 31-year-old asked to use her hose to clean a van and whether she had "seen the news".
Mr Lamarre-Condon has pleaded not guilty to the murders of Jesse Baird and Luke Davies in February 2024.
Beau Lamarre-Condon met up with a former police colleague days after he allegedly murdered a Sydney couple and told her he had "done something bad" before asking to use her hose and cleaning a van, a jury has heard.
Mr Lamarre-Condon is accused of murdering Jesse Baird and his boyfriend Luke Davies in Mr Baird's Paddington share house on February 19, 2024.
The 31-year-old allegedly used his police pistol to shoot the pair before disposing of their bodies at rural Bungonia, south of Sydney, in surfboard bags.
He has pleaded not guilty and is arguing self-defence, with his lawyers flagging an alternative version of what happened inside the Brown Street terrace involving two separate struggles with the gun.
Jurors have this week seen a video of Mr Lamarre-Condon handing himself in at Bondi Police Station on February 23, 2024, four days after the alleged murders.
The court on Wednesday heard evidence from a former colleague of the accused, known by the pseudonym Fiona Rosso in the trial, who said Mr Lamarre-Condon stopped at her home unexpectedly on the evening of February 22.
"He started crying and he said words like … 'I came to say goodbye'," Ms Rosso told the court.
She recalled him also saying: "I've done something bad but I don't want to incriminate you, I won't tell you, can I use your hose?"
Ms Rosso said the accused asked whether she had "seen the news" and asked her to search for Mr Baird's name, which resulted in her seeing articles about Mr Baird and Mr Davies going missing.
"I was in shock, I was like, 'I don't know what's happening here'," Ms Rosso testified.
She told the court Mr Lamarre-Condon began asking her about schizophrenia and asked her to search for the definition of it.
She said he spoke about an "out of body experience" and having "no control", along with how it had been "hard" working in the police force and the associated trauma.
Ms Rosso recalled Mr Lamarre-Condon taking a bucket to a sink and filling it, before going outside to a van which still had the rear door up.
CCTV footage showed Mr Lamarre-Condon inside Bunnings. ( Supplied: NSW Supreme Court )
She testified that she sat in the gutter and watched as he was "scrubbing".
"Out there or inside he said there was a bit of blood he had to scrub off, and he couldn't get it off," she said.
"I didn't look into the van, I just remember sitting there like, 'what the f***'."
Ms Rosso became visibly emotional during her evidence about that evening. Her voice became higher at points and her hands appeared shaky as she held them up on a video link.
She testified that Mr Lamarre-Condon mentioned an occasion where he was at Mr Baird's house showing Mr Baird his gun, and that Mr Baird had accidentally let off a round.
The bodies of Jesse Baird and Luke Davies were found near a property in Bungonia. ( Instagram )
She said the two sat on the couch and Mr Lamarre-Condon read news articles.
She recalled him speaking about "floating on a dam" that morning, but was unsure if he was saying he was at the location or describing a dream.
She said he mentioned an attempt to sink the bodies, which would not sink, and a drive of two hours or more with a girl to a farm.
"He said he had to centre himself, clean up his mess and get on with it," Ms Rosso said.
"I wanted to ask questions but I didn't want to ask too much, because I didn't want to push him."
Ms Rosso has also given evidence that in the lead up to the incident, Mr Lamarre-Condon had twice asked if he could hire a van in her name.
Mr Baird and Mr Davies died at a house in Paddington. ( ABC News: Simon Amery )
She said in the weeks prior, he met up with her to practice lines because he had become interested in acting, and made a comment asking whether she would "hide a body" for him.
She said she replied "of course mate" and interpreted it as banter or an expression of love or caring for someone.
The Crown's case is that the accused developed an obsessive and jealous infatuation with Mr Baird after they were romantically involved in parts of 2023, and that Mr Lamarre-Condon had allegedly stalked Mr Baird in the months leading up to the incident.
