Updated

The sister of a woman who was found dead with her ankles and wrists bound at a suburban San Diego mansion says investigators have ruled the death a suicide.

Mary Zahau-Loehner said Thursday that she was unconvinced when San Diego County sheriff's investigators explained their findings during a visit to her home in St. Joseph, Mo.

Sheriff's department spokeswoman Jan Caldwell declined to comment.

Zahau-Loehner said she spoke with her sister the night before her body was found and she gave no indication that she planned to take her own life.

Zahau was found dead July 13 in the Coronado home, two days after a 6-year-old boy under her care was seriously injured in a fall down the stairs.

The results of an investigation into the mysterious hanging death of a pharmaceutical CEO’s girlfriend at his Southern California mansion will be released on Friday, the San Diego Sheriff’s Department said Thursday in a written statement.

Authorities have been probing the death of Zahau, who was found July 13 hanging by her neck -- naked with her hands and feet bound -- from a balcony inside the mansion of Jonah Shacknai, chairman and chief executive of the Medicis Pharmaceuticals.

Zahau, who was dating Shacknai, was found dead two days after his young son, Max, 6, fell down a staircase inside the historic home on the San Diego Bay. The child died from his injuries days later at a hospital.

Mary Zahau-Loehner, the woman's sister, said in statement to KFMB-TV in San Diego that she does not believe her sister took her own life. But local news reports indicate that Zahau may have grown depressed because she reportedly was watching the boy when he fell.

Police have called Zahau's death "bizarre" and said they're investigating whether it was a suicide or a homicide.

Shacknai's brother, Adam, who was staying in the mansion guesthouse at the time, found Zahau's body in the early morning on July 13 and called 911. He reportedly cut the rope in an attempt to save her. His brother, Jonah, was not at home, according to reports.

The sheriff will be joined at a news conference Friday by the county’s medical examiner and other police officials.

The Associated Press contributed to this report.