A billionaire couple’s “lock box” is expected to provide key clues into their gruesome deaths by strangulation six weeks ago after Toronto police confirmed they were investigating a double murder.

Homicide detectives said on Friday that 75-year-old Barry Sherman and his wife Honey, 70, were not the victims of a murder-suicide, as initially speculated in media reports that outraged the family.

Barry was said to be worth £2.7 billion from his drug company Apotex and the couple had become major philanthropic and social figures in the country’s Jewish community.

But the case shocked the country after police confirmed their bodies were found with belts tightened tautly around their necks, reclining in a semi-seated position from a metal bar on their knees at their home’s lower-level indoor pool.

There was also evidence that their hands had at one point been bound.

“I believe they were targeted,” Detective-Sergeant Susan Gomes told journalists on Friday.

Speculation over the deaths has been rampant since the Shermans’ bodies were discovered on December 15 last year, just hours before the onset of Shabbat.

The Jewish community was stunned and traumatised at news of the high-profile deaths, but that was quickly replaced by speculation.

The Shermans’ children ordered a second autopsy and hired private investigators to shadow the police inquiry.

At the home, which had been up for sale, there were no signs of forced entry. But homicide investigators are poring over 127 witness statements and have gathered four terabytes of digital security files containing 2,000 hours of video footage from homes and businesses near the Shermans.

Significantly, the police have possession of a realtor’s “lock box” containing a detailed record of visitors to the Sherman home over the last months – “important to us, absolutely,” Ms Gomes said.

Speculation also revolved around how numerous Barry Sherman’s enemies might have been.

His reputation was that of a tough businessman who used the courts freely to break patent protection and make way for his generic drugs in the market.

But he was known to have made enemies in the process.

“They hate us,” Sherman said in a 2000 interview, apparently referring to the brand-name pharmaceutical industry.

“They have private investigators on us all the time, trying to investigate.

“The thought once came to mind, why didn’t they just hire someone to knock me off. For a thousand bucks paid to the right person you can probably get someone killed.

“Perhaps I’m surprised that hasn’t happened.”