TORONTO -- Police said Friday they believe Canadian drug-company billionaire businessman Barry Sherman and his wife were both murdered.

Det. Sgt. Susan Gomes said investigators came to the conclusion after six weeks of investigation, but declined to discuss possible motives or suspects.

The founder of generic drugmaker Apotex and his wife, Honey, were found dead in their mansion on Dec. 15. Police said then the deaths were suspicious, but said there were no signs of forced entry and they were not looking for suspects.

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The day after the bodies were found, prominent media outlets quoted unidentified police officials as saying it appeared to be a murder-suicide. But that theory was never publicly confirmed by authorities and family said that would have been wildly out of character.

Gomes said the two were found hanging by belts from a railing that surrounds their indoor pool. She said they were in a semi-seated position on the pool deck.

"We have sufficient evidence to describe this as a double homicide investigation and that both Honey and Barry Sherman were in fact targeted," Gomes said.

She said were last seen alive in the evening hours of Wednesday Dec. 13 and were not heard from again until their bodies were found late Friday morning.

Gomes said there are no signs of forced entry at access points of the home. She declined to discuss the evidence, possible motives or suspects.

The couple's four adult children have hired their own team of investigators and a pathologist, who conducted second autopsies on the Shermans.

Toronto police investigators have scoured the 12,000-square-foot home, hauled away the couple's cars and even checked the sewers in one of Toronto's most exclusive neighborhoods for clues.

Sherman was a fiercely competitive businessman, once musing that a rival might want to kill him.

Sherman, 75, was known for litigiousness and aggressive businesses practices as he developed Apotex Inc., which has a global workforce of about 11,000. He conceded he made enemies in "Prescription Games," a 2001 book about the industry.

"The branded drug companies hate us. They have hired private investigators on us all the time," he said. "The thought once came to my 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."

Canadian Business magazine recently estimated his worth at 4.77 billion Canadian dollars ($3.65 billion), making him the 15th richest person in the country.

As they became wealthy, the couple became known for philanthropy. They gave tens of millions to the United Jewish Appeal, donated to a geriatric hospital in Toronto and sent medicine to disaster zones. Prime Minister Justin Trudeau attended the funeral and Sherman is posthumously due to receive one of the country's highest civilian honors this year.

Friends and family say the couple had been making plans for the future. They had recently listed their home in Toronto for 6.9 million Canadian dollars and they were building a new home in the city.

Police have released the home back to the family.

"For them it's been difficult to balance their patience with their frustration with us and our investigation - not unlike any other family who have suffered such a sudden and profound loss," Gomes said. "They have been understanding, cooperative and hopeful that this investigation can give them some answers."