His estranged wife's brother had been shot dead. The home of a judge presiding over his bitter custody dispute had been levelled by an explosion. And the wife of another judge, who restricted him access to his daughter, was dead after a bomb exploded at her front door.

The series of violent events allegedly prompted work colleagues of Leonard John Warwick, a firefighter living in Sydney's south-west, to remark to him that he might be the one responsible for this campaign of terror.

And when most of the staff left the room, Mr Warwick allegedly said to a colleague: "They're after me but they'll never get me".

Thirty-one years later, the now 68-year-old Mr Warwick appeared in Campbelltown on Thursday charged with 32 offences, including four murder chargers.

The offences relate to a string of bombings and shootings targeting judges of the Family Court, his ex-wife's family and members of the public.

He did not initially wish to appear before the court but Magistrate Robert Rabbidge ordered it was in the public interest for Mr Warwick to be brought into the dock.

Dressed in a purple pullover and blue denim jeans, his grey hair cropped and with a moustache, the ex-firefighter appeared to take in everyone sitting in the packed courtroom before sitting quietly.

Documents tendered to the court during his brief mention, state that police will allege his motivation for the attacks between 1980 and 1985 was his divorce proceedings in the Family Court and his "intense desire to have custody" of his young daughter, Trudi and ownership of the matrimonial home.

A long-time suspect, Mr Warwick was arrested on the treadmill at a rehab gym at Campbelltown on Wednesday while his home in nearby Douglas Park on Sydney's outskirts was raided.

"I was with another lady on the treadmills and I just happened to look out the door and told her there were a lot of detectives standing outside," a woman using the gym at the same time told Fairfax Media. "We watched them come in and they walked over to the bloody line of treadmills right in front of us."

The arrest followed a decision by the NSW police's unsolved homicide team to restart investigations into the four murders and five bomb attacks that tore through the homes of judges and a Jehovah's Witness congregation.

The police documents before the court allege the threats of violence by Mr Warwick started in April 1979, when his ex-wife came to collect their daughter.

Mr Warwick allegedly told her: "You know that I can shoot your father at anytime". He then told his wife that she would be next.

Police allege that in February the next year, Mr Warwick intended to murder his ex-wife's father in a bid to intimidate her to cease the Family Court proceedings, but instead killed her brother, Stephen Blanchard.

It is alleged that Mr Warwick then shot dead a Family Court judge David Opas​, flattened the home of another judge who narrowly escaped with his young children, and planted a bomb outside the home of a third judge, Ray Watson, that killed his wife Pearl.

The ex-firefighter is also accused of bombing the Family Court building at Parramatta, trying to blow up a solicitor, and with planting the explosive that ripped through the Jehovah's Witness Kingdom Hall at Casula, killing a father-of-three and injuring dozens.

Police will allege that DNA found on the carpet and a piece of cardboard at the Kingdom Hall was tested and compared with a sample of blood from Mr Warwick's daughter, Trudi.

"It has been determined that the blood found in the Kingdom Hall is consistent with the paternal lineage of Trudi, and therefore the accused," police documents state.

Detective Chief Inspector Pamela Young, who headed the investigation by the unsolved homicide squad, said on Thursday that DNA evidence was just one part of the brief.

She said some witnesses who gave scant evidence before, possibly fearing for their safety, had now given expanded accounts, which helped lead to Wednesday's arrest.

"[That's why] we haven't announced what we have been doing along the way so I imagine a few people are surprised," she told reporters after Thursday's brief court proceedings.

"We have been working a long time for the victims and the community in the shadows and now we are very happy to have our case listed by the courts."

Mr Warwick did not apply for bail on Thursday and it was formally refused. The matter returns to court next week.