The 31-year-old calmly stepped into the witness box to testify at his NSW Supreme Court double murder trial on Thursday.
He is expected to give his own version of how couple Jesse Baird and Luke Davies were shot and killed in their urban terrace.
As the only witness to the deaths, the former police officer has denied entering their Sydney terrace in February 2024 with an intention to kill.
He began his testimony being asked by defence barrister John Stratton SC about trauma he experienced as a police officer. "Did you have to deal with dead bodies?" the barrister asked.
"Many times," Lamarre-Condon replied.
He described seeing a man shot in the head with a shotgun, an Uber Eats driver who had his head run over by a truck, and a man pushed from his balcony to be impaled by a metal pole.
His voice started cracking as he described a male police officer who died by suicide at Surry Hills police station.
"I had a conversation with him not long before his death," he said.
"Nothing appeared out of the ordinary for me."
He also recounted bullying at the hands of his superior officers, including one who said police should be able to push gays off cliffs like in the old days.
The 31-year-old described how he met Mr Baird in October 2022 at a nightclub on Sydney's Oxford Street.
The pair were initially "friends with a sexual relationship" but then started dating in December that year, he told the jury.
They continued dating in 2023, but the relationship ended acrimoniously at the end of the year.
Lamarre-Condon is set to allege he entered the terrace disguised as an Uber Eats driver and carrying his police-issued firearm in February 2024 to retrieve his belongings.
He was then surprised by Mr Baird who did not recognise him with a motorcycle helmet on.
The pair physically struggled and Lamarre-Condon's gun went off, killing the TV presenter, Mr Stratton has previously said.
The 31-year-old claims Mr Davies then picked up the gun, fatally shooting himself.
Lamarre-Condon's offer to plead guilty to the manslaughter of Mr Baird was rejected by prosecutors.
He has pleaded not guilty to two charges of murder.
Prosecutors allege Lamarre-Condon 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.
Days after their deaths, he led police to a rural monastery where the bodies of the two men, both aged in their 20s, were found in surfboard bags.
His testimony continues.
Lifeline 13 11 14
beyondblue 1300 22 4636
22°C