By Alex Tresniowski
August 15, 2011 12:00 PM

On July 11, Ted Greenberg took an unusual phone call from a woman who was crying and distraught. “She said, ‘I need someone to take care of my dog. There’s been an accident,'” recalls Greenberg, owner of Camp Diggity Dogs, a boarding center in San Diego. “She said her child was in a coma.” The next day, Greenberg met the woman, Rebecca Zahau, in her home in nearby Coronado to pick up Ocean, her Weimaraner. Zahau, 32, “wasn’t in distress or erratic, just very subdued,” says Greenberg. “She was very quiet. Almost eerily quiet.”

Less than 24 hours later, Rebecca Zahau was dead, and the house-the fabled 103-year-old Spreckels mansion-was the scene of a second shocking tragedy in just three days. First, on July 11, the 6-year-old son of pharmaceutical tycoon Jonah Shacknai, the mansion’s owner, was found at the bottom of a staircase, not breathing and without a pulse; the boy, Max, later died of his injuries. Then, on July 13, police were again summoned to the mansion-a 27-room waterfront marvel built for industrialist John D. Spreckels and purchased by Shacknai in 2007 for $12.7 million. This time they found the naked body of Zahau, Shacknai’s girlfriend, in the courtyard; her hands and feet had been bound and she’d been hanging from a second-floor balcony, a noose around her neck. The two mysterious deaths have stunned the posh beachside community and confounded local police. “The case is certainly suspicious,” says Sgt. Roy Frank of the San Diego sheriff’s homicide unit. “It is not usual to find a female in a backyard unclothed and tied up. That, combined with Max’s accident, makes it suspicious.”

So far police haven’t been able to definitively answer two big questions: Are the deaths of Max and Zahau connected? And did Zahau kill herself, or was she murdered? It was Jonah Shacknai’s brother Adam who called police at 6:45 a.m. on July 13; he said he’d found Zahau hanging from the balcony and cut her down. There was apparently no evidence of a break-in or struggle, suggesting, at least initially, a suicide. But if she did kill herself, why did she first bind her feet and hands-behind her back, no less-and why was she naked? “I’ve never seen a suicide victim on display like that, in the nude,” says former San Diego homicide detective Richard Carlson, a 35-year police veteran. “And it’s one thing to tie your hands to prevent saving yourself, but why tie your feet?”

The man at the center of the mystery-Jonah Shacknai, 54-is chairman and CEO of Medicis Pharmaceutical Corporation, an Arizona-based firm that pulled in $700 million in net revenues in 2010 (his salary was $6.3 million). In 1993 he married pharmaceutical sales rep Kimberly James; they had two children (now ages 13 and 14) before going through a contentious divorce that was settled in 2001. “During the marriage and after the divorce, he was always a great father,” says someone close to Shacknai. “The most important thing in his life is to be there for his kids. He doesn’t run wild with his emotions; he’s a very even-tempered person.”

Yet Shacknai’s second marriage-to psychologist Dina Romano-was marked by police complaints on both sides and allegations of abuse. Romano claimed she was attacked by Shacknai’s German shepherd during arguments, and that Shacknai was “not quick to pull the dog away,” she told police. “I feel scared of what he is capable of doing to me physically via the dog as well as the lengths he will go to try to destroy me.” Shacknai told cops he was “assaulted physically several times” by his wife. The former couple have said in a statement that the police report did not accurately reflect what occurred, and that they have since worked out their differences. Indeed, after their 2008 divorce they agreed to share custody of Max and live just blocks apart in Coronado.

Around that time Shacknai began dating Rebecca Zahau, a native of Burma who spoke several languages and worked as a certified ophthalmic technician. “She was such an incredibly optimistic, positive, driven person,” says Dr. Felicia Popowski, 36, Zahau’s good friend and former colleague. Zahau’s divorce from her first husband, Neil Nalepa, a nursing assistant, was finalized in 2011-two years after she began seeing Shacknai. Zahau and Nalepa “just weren’t that compatible,” says Popowski. “It had nothing to do with money. It was more about her yearning for an equal partner.”

By all accounts she found just that in Shacknai. “Jonah was very devoted to her,” says Zahau’s brother-in-law Doug Loehner. “She treated his kids as her own.” Then came July 11 and Max’s fatal fall. Police have not yet determined if Max might have fallen over the staircase railing, but for now they don’t suspect foul play. Shacknai and his ex-wife kept a vigil for Max at San Diego’s Rady Children’s Hospital until he died on July 16; by then Shacknai’s younger brother Adam had flown in from Memphis to lend support and was staying at the mansion. In many ways the opposite of his brash, successful brother, Adam, 47, worked as a tugboat captain, never married and lives alone. “He’s very easygoing, very smart and loves his family,” says a relative. One Memphis neighbor called Adam introverted: “He talks if you initiate a conversation, but otherwise keeps to himself.”

Authorities consider Adam “an important witness,” says Sergeant Frank. “He has information that can help solve this mystery.” Frank also says police are looking into the stories of “anyone associated with the mansion. We’re checking the consistency of everyone’s statements.” Shacknai, his ex-wife and brother have all been cooperative, say police. “Jonah would never harm Rebecca or Max,” insists his friend Mary Clark, 50. “He is just a victim of two horrible tragedies.”

What kind of tragedies they were, however, will take some time to sort out; the results of forensic tests on Zahau’s body are still weeks away. For now, that leaves only sadness and questions. “No way was it a suicide; she would never do that,” says Zahau’s close friend Lori McCoy. “I’m trying to keep an open mind and not put blame on anyone. But something happened in that mansion. We just don’t know what.”