The former police officer has pleaded not guilty to murdering Jesse Baird and Luke Davies in Mr Baird's inner-city Sydney terrace on February 19, 2024.
Lamarre-Condon, now 31, later led officers to a rural property where the bodies of the two men, both aged in their 20s, were found in surfboard bags.
At the time, Lamarre-Condon was dating a South African man, Juan-Roux Zwaan, and the pair chatted over Instagram on the day of the alleged murders.
"I'm sorry I've been a bit MIA," the accused killer said in a voice message.
"It's just one of those weeks. I'm just trying to get back into a positive mindset."
"I'm in bed at the moment, I'm just not feeling the best hey."
Mr Zwaan's statement and the audio recordings were heard by a NSW Supreme Court jury on Tuesday.
In his messages, Lamarre-Condon spoke about cancelling a boat party and refraining from going to the gym, but he said he would attend a Taylor Swift concert the weekend after.
It was not the first time the hit singer was mentioned in the trial.
In his statement, the former police constable also described a friend referring to the Swift song No Body, No Crime after seeing two bodies in the back of a white hire van.
The day after the men were allegedly murdered, Lamarre-Condon told Mr Zwaan he would have to miss a bottomless lunch as he wanted to look after his health.
When asked why he had shut down his Instagram, the then-police officer said he wanted to take a mental break as it was addictive.
The 31-year-old said he had a day operation and sent a photo of himself from a hospital bed on February 21.
It was the last time Mr Zwaan heard from Lamarre-Condon, who handed himself into police two days later.
Earlier on Tuesday, the court heard Mr Baird, a TV presenter, had been hired by television firm Breakout Productions to film a shark documentary in Sydney, starting on February 19
"I thought he was amazing," company co-owner Lana Thrupp wrote in a police statement read out in court.
"I knew after speaking with him I wanted to hire him."
An excited Mr Baird thanked her for the opportunity, she wrote.
However, Ms Thrupp began to worry when he then failed to answer his emails or answer her calls, the jury heard.
Late at night on February 20 - a day after Mr Baird was killed - she received a text message from his mobile number.
"Hey Lana sorry to do this for you but after a lot of thought I thought it would be best to resign effective immediately," the message read.
"I hope you understand thanks."
The jury previously heard Lamarre-Condon took Mr Baird's phone and used it to send various messages, including to the 26-year-old's housemates implying he was taking a road trip to Perth.
Lamarre-Condon and Mr Baird broke up for a second time in November 2023 after the then-cop wanted an exclusive relationship, according to prosecutors.
The TV producer did not want the same thing, the jury was told.
Lamarre-Condon allegedly killed Mr Baird "execution-style" at close range through a plan borne of a jealous obsession, before shooting Mr Baird's new partner Mr Davies to eliminate a witness.
The former senior constable claims he killed the men in self-defence after entering their terrace disguised as an Uber driver to retrieve his belongings.
His offer to plead guilty to Mr Baird's manslaughter was rejected by prosecutors.
The trial continues.
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