Rebecca Zahau
© unknownRebecca Zahau's family doesn't believe her death was a suicide.
Rebecca Zahau, the girlfriend of pharmaceutical executive Jonah Shacknai who committed suicide at his Coronado mansion, was distraught over injuries his son suffered in her care and that is apparently why she decided to hang herself, authorities said Friday.

Zahau's nude body was found in the courtyard of the historic Spreckels mansion on Ocean Boulevard on the morning of July 13. Her hands and feet had been loosely tied, and a noose was around her neck and tied to a second-story balcony, officials said.

Although how she killed herself may seem unusual, it is not unprecedented and there is no evidence that there was foul play, San Diego County Sheriff Bill Gore said at a Friday morning news conference.

Her fingerprints and DNA were the only ones found on the rope as well as the knife she used to cut it into pieces and place sections around her feet, hands and around her neck, Gore and other authorities said. Investigators also conducted an experiment with a woman of similar size to see if she could tie herself up in the same way with the same knots, and they concluded that she could, authorities said.

"Science does not lie," Gore said.

Zahau, 32, also had taken some black paint and painted a message on the door to a guest room where she had been staying, authorities said, declining to reveal what the message was. Toxicology tests revealed that there was nothing in her system that would have impaired her judgment, they said.

Investigators said they spoke to someone who knew Zahau and that that person said she had been upset for months, was losing weight and not exercising. They described Zahau as being 5-foot-3 and weighing 100 pounds at the time of her death. Authorities also said they found notes in Zahau's personal journal indicating emotional distress.

The evidence is "compelling" and points "persuasively" to suicide, Gore said.

Zahau was despondent over a sense of responsibility for the injury suffered by Shacknai's 6-year-old son Max during a time when Zahau was supposed to be watching him, authorities said. The boy fell down a staircase and landed on his head, authorities said. After a week in the hospital, he died on July 17 from his injuries.

His death was ultimately ruled an accident.

But about 1 a.m. on July 13, Zahau got a call from someone informing her that the boy's injuries were worse than originally thought and that he would likely die, authorities said. It was at that point, officials said, that they believe she decided to commit suicide.

Forensic evidence indicates that she killed herself shortly before 3 a.m. Her body was found about 6:40 a.m. by Shacknai's brother, Adam, a guest at the mansion. Jonah Shacknai, 54, was not home at the time.

Mary Zahau-Loehner, Rebecca's Zahau's sister, had told reporters Thursday night that the family does not believe Zahau took her own life.