The bodies of Jesse Baird, 26, and Luke Davies, 29, were found inside surfboard bags at the fence line of a rural property in Bungonia near Goulburn, about 200km southwest of the city, on Tuesday.
Lamarre-Condon, 28, is behind bars after being charged with murdering the couple at Mr Baird's home in Paddington in Sydney's east on February 19.
Police will allege Mr Baird's murder was premeditated and believe Mr Davies was in the wrong place at the wrong time.
"We will be strongly claiming in our case that this murder was premeditated and the second murder occurred because of, unfortunately, Luke's presence at the house," Assistant Commissioner Michael Fitzgerald told Nine News.
The men were allegedly shot by Lamarre-Condon, a senior constable in the NSW Police, with a police-issued firearm before their bodies were transported to the rural property.
Police allege that two days before the killing the constable purchased a surfboard cover a store at Miranda in Sydney's south with the intention to carry Mr Baird's body but after allegedly killing both men one bag was not enough.
"Following the incidents and the murders, he went back and bought a further surfboard cover," Mr Fitzgerald said.
Police Commissioner Karen Webb confirmed the officer has been served a notice for his dismissal from the force.
"I've actually today read a segment of his file and I have signed - and it has been served, he has been served today in custody - a show-cause notice for his dismissal," Ms Webb told ABC 7.30 on Wednesday night.
Floral tributes have heaped up outside the inner Sydney home wehre two young men were slain. (Bianca De Marchi/AAP PHOTOS)
Domestic violence rates within the LGBTQI community are being highlighted in calls for further police training to address the issue following the alleged murders.
Investigators allege the crimes followed a months-long campaign of "predatory behaviour" by the charged officer, culminating in the fatal shooting.
Peter Murphy, who took part in the first Mardi Gras march in 1978, said LGBTQI communities were not immune from domestic and family violence.
But many gay and lesbian people were hesitant to report it to police due to historical discrimination displayed by the force, he added.
"Personal relationships, whatever genders are involved, can have an ugly side," Mr Murphy told AAP.
"I don't think there's enough training within the police on these matters and in the next few months, I think we'll see a fairly good effort from police but it can fade off easily.
"If the police response to this is more of a public relations exercise, everyone will be disillusioned."
NSW Greens MP Amanda Cohn said the pain and grief of queer communities in NSW was tangible.
"Parts of the community don't feel safe reporting threats or violence to police," she said.
"The NSW Police continuing to investigate themselves cannot deliver the meaningful change that is needed.
"Only an independent review of the institutional approach to policing can deliver the transparency and accountability the community needs to build trust."
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