SAN DIEGO -- Footprints spotted on a dusty balcony and traces of DNA found on knives and pieces of rope helped investigators conclude that the mysterious death of a woman found hanging naked at a historic California mansion was a suicide, authorities said Friday.
The overwhelming physical evidence suggests that Rebecca Zahau bound her ankles and wrists, tied a rope around her neck and hung herself from the balcony of her pharmaceutical tycoon boyfriend's home in suburban San Diego in July, San Diego County Sheriff Bill Gore said.
Zahau, 32, was discovered dead six hours after she retrieved a voice mail that her boyfriend's 6-year-old son condition had suddenly worsened and that he was unlikely to survive, investigators said.
The boy, Max Shacknai, had suffered injuries days earlier in a fall down the mansion's stairs. He later died from his brain injuries in a fall that authorities ruled an accident.
"Was Max's death a homicide? The answer is no," Gore said at a news conference. "It was a tragic accident. Was Rebecca's death a homicide? Again the answer is no. It was a suicide ... These deaths were not the result of any criminal acts."
Other evidence included fingerprints and a message in black paint left by Zahau on the bedroom door, Gore said. He declined to disclose the message's content and stopped short of calling it a suicide note.
The woman and the boy are linked to Jonah Shacknai, founder and chief executive of Medicis Pharmaceuticals Corp. and owner of the 27-room waterfront mansion. Zahau was his girlfriend of two years. Max was his son from a marriage that ended in divorce in 2008.
"Nothing will ever be the same for our families after these losses, but with today's information providing some much needed answers, we will try to rebuild our lives and honor the memories we carry with us," Shacknai said in a statement.
No one saw Max Shacknai fall, but Zahau was home with her 13-year-old sister and heard a loud noise, investigators said.
Investigators believe the boy fell over a railing of a U-shaped staircase, struck a chandelier and hit another railing before falling on his face. He was found near broken chandelier glass, two soccer balls and a scooter.
The boy injured his neck, which stopped his heart and breathing for about 30 minutes, said Dr. Jonathan Lucas of the San Diego County Medical Examiner's Office. The lack of oxygen to his brain caused irreversible damage and his death five days later.
Two days after the boy's fall, Shacknai's brother, Adam, called 911 to report that Zahau appeared to be dead, investigators said. The brother was staying in a mansion guesthouse. Jonah Shacknai was not at home.
Friday's 1 1/2-hour news conference included a video reenactment of how investigators think Zahau bound her wrists.
They believe she used two knives to cut rope that she tied to bedposts and around her wrists and ankles, Gore said. She loosely bound her wrists, took one arm out and put both arms her back before tightening the noose, he said.
Zahau's DNA was found on the rope and the bedposts, her fingerprints were on the bedposts and her footprints were on the balcony. The knives were recovered in the bedroom, one with her DNA and another with her fingerprints, Gore said.
"We don't know exactly how this event occurred," sheriff's Sgt. Dave Nemeth said. "We don't know in what order things were done. The only person who can answer that question, unfortunately, is deceased."
Zahau's sister criticized authorities for ruling the death a suicide. Mary Zahau-Loehner told The Associated Press Thursday that her sister gave no hint that she planned to take her life when they spoke the night before. Zahau said she would bring Jonah Shacknai breakfast and a change of clothes the next morning to the hospital where his son was being treated.
Gore noted that the sister's call came before Zahau learned that Max Shacknai's condition suddenly worsened.
"It's unfortunate she can't accept the results. These are the results to the best of our ability," he said.
Lucas, who conducted the autopsy, said he was confident in the findings.
"I'll be the first to admit that this was a unique and unusual case," he said.
One witness, who authorities declined to identify, said Zahau didn't look good, had stopped exercising and appeared to have lost weight in January, Gore said. Investigators also discovered a lengthy "journal" stored in her phone that also indicated she was unhappy.
Zahau-Loehner said the family had many unanswered questions after investigators visited their home in St. Joseph., Mo., on Wednesday to deliver the findings. Her family has hired Seattle attorney Anne Bremner.
Zahau, a native of Myanmar, was an ophthalmic technician at Horizon Eye Specialists & Lasik Center in the Phoenix area from April 2008 to December 2010. Her sister described her as a religious person.
Shacknai has been chairman and chief executive of the Scottsdale, Ariz.-based Medicis since 1988. The company makes acne treatments Solodyn and Ziana and facial wrinkle treatment Restylane and Dysport, a competitor of Botox.
Shacknai bought the mansion, known as the Spreckels mansion, in March 2007, when it was assessed at $12.75 million. The home was built in 1908 and named for its original owner, John D. Spreckels, who also owned the San Diego Union and San Diego Tribune newspapers.