An officer accused of killing his ex-partner and his new boyfriend went to extraordinary lengths to cover up his crimes, criss-crossing hundreds of kilometres around Sydney in the days after the murders, police say.

The alleged crimes of Senior Constable Beaumont Lamarre-Condon followed a months-long campaign of “predatory behaviour”, culminating in a fatal shooting at an inner-city home a week ago, investigators say.

NSW Police believe the 28-year-old acted alone but divulged “partial admissions” to others in the days before he handed himself in to police over the disappearance of former Ten reporter Jesse Baird, 26, and Qantas flight attendant Luke Davies, 29.

Lamarre-Condon is accused of using his police-issued firearm to murder the couple after using a key to access Mr Baird’s Paddington home last Monday.

A triple-zero call was made from Mr Baird’s phone about four minutes after shots were heard at the property, but the call disconnected before anyone spoke, Deputy Commissioner David Hudson told reporters on Monday.

Lamarre-Condon then allegedly used Mr Baird’s’ phone to delete messages and posed as the deceased to throw investigators off track.

In one message, he asked the 29-year-old’s flatmates to put his possessions in storage after conjuring an elaborate story that Mr Baird would be moving to Perth, Mr Hudson said.

Lamarre-Condon, who was previously in a relationship with Mr Baird, then allegedly made attempts to clean the crime scene before hiring a van to move the bodies.

An “innocent friend” unknowingly assisted him when he allegedly disposed of their bodies, Mr Hudson said.

“There are two acquaintances that we believe the accused spoke to – one was a former officer, the other was not,” he said.

Lamarre-Condon also made contact with family members and police were relying on their assistance as part of the investigation, Mr Hudson added.

“There were certain admissions – partial admissions – made … however, the information at the time was not passed on to police,” he said.

Police on Sunday began searching dams at a property in Bungonia, an area near Goulburn and almost 200km southeast of Sydney, as they try to find the missing couple’s bodies.

Officers were pointed to the Southern Tablelands property after discovering “an innocent agent” travelled there on Wednesday afternoon with Lamarre-Condon in a hired van.

An angle grinder bought earlier by the acquaintance was used to cut a padlock on a gate, before Lamarre-Condon travelled alone into the property, returning about 30 minutes later, police allege.

The pair made the two-hour trip back to Sydney only for the accused to allegedly purchase weights and return to the property later that night.

Gaps in the timeline of Lamarre-Condon’s movements last week left open the possibility he retrieved the bodies and disposed of them somewhere else, police allege.

“It would appear that the accused was suspicious of the acquaintance that attended with him and about her belief that what he might have been up to, and very likely may have returned to those bodies later that evening,” Mr Hudson said.

The acquaintance was not a suspect and did not know that two bodies were allegedly in the back of the hired white van.

Lamarre-Condon was next seen leaving the area about 4.30am on Thursday for Sydney, before heading to another acquaintance’s property in Newcastle.

“Without fully disclosing any criminality, he asked for access to a hose to clean that van,” Mr Hudson said.

Divers had previously been seen searching a waterway at Lambton, Newcastle.

Mr Hudson said officers were also aware of “indicators of predatory behaviour by the accused” in the months before the murders.

The relationship between him and Mr Davies “did not end well”, he added.

Lamarre-Condon, who joined the police force in 2019, is in custody after not making a bail application on his initial court appearance for the twin murder charges.

The couple’s disappearance was deemed suspicious when blood-stained possessions belonging to them were found in a skip in the southern Sydney suburb of Cronulla on Wednesday.

The discovery led police to Mr Baird’s blood-smeared share house, about 30km away.

Mourners continue to lay floral tributes outside the Paddington terrace where police allege the murders took place.