Christopher Bouggas, 41, has been charged with two counts of murder after the bodies of Steven Finlay, 52, and his partner Mitch Watson, 32, were found at the unit on Cleveland Street, Redfern, shortly before midnight on Saturday.
Detective Superintendent Rodney Hart said one of the victims was on the phone to triple zero whilst police were en route to the property for a welfare check.
He said it had been a difficult and confronting scene for officers and both the victims had suffered significant injuries.
Strike Force Menlow was quickly set up to investigate the incident, and Mr Bouggas was arrested at a Redfern unit on Cleveland St on Monday afternoon.
It is believed he was also a tenant of the boarding house.
Mr Bouggas was taken to Mascot police station and charged with two counts of murder. He did not appear in court on Tuesday afternoon when his matter was mentioned. He was formally refused bail and the case was adjourned to March 29.
Anyone with information that may assist police is asked to contact detectives at Mascot police station or call Crime Stoppers on 1800 333 000.
Source: The Sydney Morning Herald.