Constable Beau Lamarre, 28, handed himself in at Bondi police station in Sydney's east shortly after 10.30am on Friday.
Homicide Squad commander Daniel Doherty said he was due to be charged with two counts of murder following the disappearance of reporter Jesse Baird, 26, and Qantas attendant Luke Davies, 29.
The pair have not been heard from since Monday, triggering a subsequent police search for Const Lamarre, who previously dated Mr Baird.
Flight attendant Luke Davies, 29, disappeared at the same time as Mr Baird. (HANDOUT/NSW POLICE)
Their disappearance was treated as suspicious after possessions belonging to both men were found in a skip bin in the southern Sydney suburb of Cronulla on Wednesday.
That discovery led police to Mr Baird's blood-smeared share house, about 30km away in inner-city Paddington.
Detective Superintendent Doherty said investigators also found a discharged gunshot round at the home and that had been matched to a police firearm.
CCTV footage captured from a neighbouring property showed a white van outside Mr Baird's house shortly before the couple disappeared.
The van, a Toyota HiAce, was hired from Mascot on Monday night and used to transport the bodies of the two men after they were killed at the home, Det Supt Doherty said.
Detectives have appealed for information about the movements of the van, which has NSW registration CW82PM, since Monday evening.
Officers executed a search warrant and seized a number of items from a home at Balmain, in Sydney's inner west, about 11.30pm on Thursday.
Property records reportedly indicate the home was purchased under the name Lamarre.
Neighbours heard shouting at Mr Baird's Paddington home on Monday, but the incident was not reported to police until they arrived at the scene two days later.
Blood was found at the property, indicating someone had suffered a significant injury at the site, police said.
Mr Baird's WhatsApp account was active as late as Tuesday night, leading detectives to appeal for him to come forward if able.
Police investigating the disappearance of Luke Davies and Jesse Baird are looking at a line of inquiry that a third person may be able to assist with the investigation.— NSW Police Force (@nswpolice) 📷 More details: https://t.co/wtpSLsKlvj pic.twitter.com/NkAI9AyjqrFebruary 22, 2024
Police later said inquiries had led them to believe a third man may be able to assist with the investigation, adding that detectives would look into all of the couple's past relationships and associations.
Const Lamarre, who up until days ago had an active social media presence, joined the police force in 2019.
Photos posted online show the former celebrity blogger posing with dozens of A-listers including Taylor Swift, Selena Gomez, Katy Perry, Miley Cyrus and Harry Styles.
During a 2014 Lady Gaga concert, now-Const Lamarre threw a note at the singer describing her as his "saviour".
Police are looking at all the past relationships of missing men Jesse Baird and Luke Davies. (Dan Himbrechts/AAP PHOTOS)
Gaga read the note aloud, which said: "through your music, you have helped and will continue to set free many people ... Gaga, you're not just my idol but literally my saviour."
Footage of the recently graduated officer tasering a man at close range in Darlinghurst went viral in 2020, prompting an internal review.
An investigation later cleared him of any wrongdoing.
Mr Baird previously worked as a presenter on the morning program Studio 10, while lately he had taken to the field as a goal umpire for AFL and VFL games.
Photos from his and Mr Davies' social media accounts show the couple together at a Pink concert in Sydney during the week before their disappearance.
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