Jason Paul Hawkins, 46, unsuccessfully pleaded with an ACT magistrate for his freedom on Saturday morning.

Police with a NSW arrest warrant had taken him into custody at his Chisholm home the previous night, nearly six months after the "horrendous" killing of Stacey Klimovitch.

Ms Klimovitch, 61, was shot dead at point-blank range after answering her front door in the Newcastle suburb of Stockton on June 9.

The swimming teacher was at the property with her daughter and grandchild at the time.

Detectives, who formed Strike Force Backhouse to investigate the shotgun slaying, made a breakthrough last month by identifying a dark-coloured Holden Commodore sedan believed to have links to those responsible.

They released images of a similar vehicle before a major development on Friday morning, when officers arrested Hunter man Stuart Daniel Campbell, 29, in Newcastle.

NSW Police allege he "orchestrated" the killing of Ms Klimovitch, who was the mother of his former partner, and he has since been charged with her murder.

The ACT Magistrates Court heard on Saturday that investigators also planned to charge Mr Hawkins, the alleged shooter, with that offence in the coming days.

The 46-year-old Chisholm man appeared before magistrate James Lawton from a remote room within the ACT courthouse, expressing bewilderment at his situation.

He said he had "corroborated as much as possible" and unlocked his devices for police.

"I know the allegation is murder but there's no statement of facts or nothing," Mr Hawkins told the court.

"I don't understand what's happening."

The man went on to say he would "do whatever I have to do" to get bail because his daughter needed his support.

The court heard he had a criminal history and an outstanding charge of obstructing a public official from 2020, but Mr Hawkins insisted his record showed he had "changed my ways".

While Legal Aid duty lawyer Hugh Jorgensen said Mr Hawkins had instructed him to make a bail application, Mr Lawton said he was minded to adjourn the case until Newcastle detectives arrived in the ACT on Monday morning to apply for the 46-year-old's extradition.

Mr Hawkins, having been refused bail until then, again complained as he was led out of the remote room.

"No statement of facts," he said. "Nothing."

Mr Campbell was also remanded in custody on Saturday, when his case went before Newcastle Bail Court.

On Saturday afternoon, Detective Superintendent Wayne Humphrey said investigators had put in "a magnificent effort".

The Newcastle City Police District commander described the alleged murder as "an execution-style homicide".

"It was just horrendous," he told reporters.

"It doesn't get any worse than this; in front of a daughter and a grandchild. There's no such thing as a good murder, but this was just horrendous."

Detective Superintendent Humphrey congratulated the members of Strike Force Backhouse, saying investigators were initially hindered by "a total lack of obvious clues".

He said their "painstaking attention to detail" during "a very fine investigation" had resulted in Friday's arrests.

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"We will soon see, with the ongoing investigation, if any other person will be charged," the superintendent said.

"But we are more than comfortable, at this time, that we have the predominant two actors of the murder, being the person who orchestrated it and the shooter."

A 64-year-old man from Waratah West, in Newcastle, was also arrested on Thursday in respect of unrelated matters.

Detective Superintendent Humphrey said police believed that man's vehicle was used in the alleged murder, but it was too early to say whether he would also be charged.

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