TORONTO — The explosive mystery of murdered Toronto billionaires Barry and Honey Sherman is likely to be solved, says a Toronto Star journalist with a new book out about the case.

Chief investigative reporter Kevin Donovan, who has been following the case for about a year and a half, dismisses rampant speculation that the killing of the founder and former CEO of generic drug giant Apotex and his wife came at the hands of a professional hitman or international spy or over a business deal gone wrong.

Instead, in his new book “The Billionaire Murders,” Donovan says he believes the couple knew their killer or killers and that the motive was money.

“I think it’s quite likely that this was an attempt to have a conversation that went horribly wrong,” Donovan said on CTV’s Your Morning Tuesday.

The Shermans were noted philanthropists with wealth estimated at well over $4.7 billion. Barry had a reputation as a generous friend, a workaholic and an aggressive litigator in both his business and private life.

“It’s a very personal thing to strangle somebody,” Donovan said in a later interview on CTV News Channel. He said Barry Sherman was frequently known to say that if someone wanted him dead, they could shoot him as he come out of his office each night.

The Shermans’ bodies were discovered just before noon on Dec. 15, 2017 but it’s believed they were killed the night of Wednesday, Dec. 13, 2017.

Donovan says the person or people who committed the crime knew the Shermans’ movements and routines, and knew they were both home on that Wednesday night, which was unusual given their busy schedules.

Donovan says much went wrong in the investigation in the first critical 48 hours. Initially, he said, police worked on the theory that the deaths were a murder-suicide. It wasn’t until the end of January that investigators called it a targeted double murder.

The couple was found in the basement pool room of their Toronto home in semi-seated positions with belts looped around their necks from a railing beside the pool. Honey, 70, had facial injuries but Barry, 75, did not.

In the early hours and days of the investigation, police were saying there were no signs of forced entry and they weren’t looking for an outside suspect. Donovan told CTV News Channel that documents reveal police were only considering only Honey a victim of murder in the first six weeks of the investigation, indicating they believed Barry killed Honey and then himself.

“(Police) decided it was murder-suicide and then they go down this tunnel,” Donovan told Your Morning. “That’s bad for an investigation and bad for investigators. You have to look at all suspects and all possible suspects in the first 48 hours.”

Instead, Donovan documents that investigators waited months to collect DNA and fingerprints from people who had been in the home to rule them out as suspects, and some key people in the Shermans’ life weren’t interviewed until weeks after the murders. Video from security cameras in the neighbourhood weren’t viewed for more than a month, he said.

“I think the police officers assigned to the (Sherman) case were good, but there probably weren’t enough of them,” Donovan said on Your Morning.

The time the Shermans were discovered coincided with a Toronto police investigation that eventually led to the arrest and conviction of serial killer Bruce McArthur. That required tremendous police resources.

“The Billionaire Murders,” excerpts of which were published in the Star, also documents two autopsies performed on Barry Sherman’s body. The first, conducted by a pathologist with about seven years’ experience, found Barry Sherman’s death was a likely suicide because a tiny neck bone called the hyoid wasn’t snapped, long believed to be necessary to a determination of murder by strangulation.

But a second, privately hired pathologist concluded it was a targeted double murder. That finding was based on the pathologist’s previous research that showed that the hyoid doesn’t always snap during strangulation (in fact, Honey’s hyoid was not broken either), that Barry couldn’t have died by suicide in the position he was found, and that markings on the couple’s wrists showed they had both been bound at one point.

Donovan has been fighting in court to get police investigation documents unsealed, arguing on behalf of the Star that the public deserves to understand how the investigation has unfolded. Police have fought to keep search warrants and production orders secret, arguing that making them public could jeopardize their case.

At a hearing in April, Donovan says Det. Dennis Yim, the only full-time police investigator on the Sherman case, revealed under questioning that police had developed a theory about what happened to the couple. The judge intervened when Donovan asked if police had a suspect or person of interest.

Donovan says Yim responded to questioning in court this month that police are making progress in the case, that they are working on the same theory as before, and that he’s “cautiously optimistic” about making an arrest.

According to accounts in the Star, the Toronto police intelligence unit analyzed electronic records obtained under search warrants, resulting in a 41-page report given to investigators in early September. Donovan has reported that Yim said in court documents that the analysis made a “significant contribution” to the investigation and that it will likely result in more search warrants.

Yim has refused to say what kind of information has been analyzed.

The Shermans’ family have hired a private team to conduct their own investigation, offered a $10 million reward, and have had the home razed where the murders took place.