Woman and her boyfriend's son mysteriously die days apart from each other

The San Diego Sheriff's Department conclude that Rebecca Zahau's cause of death was suicide, while 6-year-old Max Shacknai's death was an accident.
9:51 | 03/03/18

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Transcript for Woman and her boyfriend's son mysteriously die days apart from each other
Here is the story. Ed body was found hanging. Reporter: The way Rebecca zaau died was straung enough. Having it happened is so shocking. Reporter: The beautiful 32-year-old found dead hanging from the balcony, naked, gagged. Authorities determine it was a suicide. It was obvious she was murdered. Who does that? No. Reporter: The family pointing fingers on the wrongful death suit. Rebecca's farmly was royalty in the country once known as Burma. She was excited about life. Reporter: A new boyfriend, he had a little boy named max. Max loved ree becca. She was extremely attentive and warm. Dana wasn't crazy about the new girlfriend. Someone else is going to be around your child. I thought we had a good working relationship together. Did you approve of the time she spent with max. I think there was times when Dina made it difficult for Rebecca. Reporter: But no one could have imagined just how difficult it was about to become. It was July 11th, in the morning. Dina had gone to work out in the gym. Rebecca was in the house with her sister. Max was on the floor. And something awful happened. The stairs. Test not breathing. Some how, 6-year-old max had Haken a horrific fall. I sprinted in the house and I saw max laying on the floor. I first saw him, he had tubes coming out of every part of his body. And I thought, wow. Did she tell you how she had the happen in. She said, what happened, I really don't know. Reporter: During the family emergency, the paints held vigil and the next day his brother flew in. He was at home. They were the only two in the house. They were exceedingly cordial. Wednesday July 13th, 2011, Adam walks into a scene of horror. Adam was the one who came out of the guest house some time after 6:30 and he saw Rebecca's body hanging from the balcony. He called 9 11. I have a girl, she hung herself. Is she still alive? A I don't notknow. Are you alive. Adam is able to cut her body died and E he is trying to E resuscitate here. Can you imagine the impact of something like that when I was already facing certainly the biggest crisis of my life. Reporter: If Rebecca had taken her own life, it was a puzzling way to commit suicide. No woman would bind their hands behind their back and jump over a balcony. 6-year-old max died -- consider the sheriff department has launched investigation. Was max's death a homicide? The answer is no. Was Rebecca's death a homicide? The answer is no. Reporter: Max's death is a freak accident. Something caused him to trip. Reporter: Investigators say it was not a homicide. DNA shows no sign that she had been attacked. Fingerprints from the balcony door and the bed were all from Rebecca. Reporter: If it was suicide, how could she tie her hands behind her back in a seemingly complicated way. Just a matter of slipping her hand out. The bindings were not tight. He treated my sister like garbage and I believe they felt like they came to a quick conclusion that Becky had something to be with max's and she deserved what she dot. Reporter: Did you ever believe that your sister was suicidal? No, Rebecca does not the have a suicidal personality at all. Reporter: Rebecca's family turned the outrage into action. The cause of death in this millionaire's girlfriend -- Reporter: Rebecca's story is on the Dr. Phil show. They exumes the body and Cyril wecht examines the body. I lean strongly towards it being a homicide. The San Diego county coroner examined it. It was on the Dr. Phil show. It's terrible. He can say it's foolish. We say it's justice. Reporter: Rebecca's family petitions to reopen Rebecca's case but in a crushing blow, the request is denied. The interest in the case remains years and years and years later. I hope somebody looks again. Reporter: It turns out someone is re-examining the case. His name is Herman wiseberg. He is a seasoned private investigators in New York City. "20/20" obtained him to investigate the case. He has things to say about what happened on the balcony. They concluded that because her footprints were on the balcony, she could have thrown herself off. But could an attacker throw her off without stepping on it and without leaving footprints. Wi Weisberg brought me to this balcony, roughly the same tice. Is this the same size? Similar, a little heavier. It's a good way to determine if I can do it. Reporter: Leall right, let's see if you can do it. It's not easy. Reporter: It's not easy but it's possible for to you not step out there. It shows that someone could have taken E Rebecca's body, put it down, leaned it against that rail and shoved it over. I'm not completely satisfied it's not a suicide but there is not evidence to show it was a homicide. Reporter: Rebecca's family wanted justice and filed Keith Greer. He filed a case. But Dina was at the hospital when Rebecca died and Greer dropped it from the suit. I think it's a disgraceful abuse of the legal system. Reporter: Now his case is targeted at Adam shacknai. You think that Adam shacknai killed your sister? Yeah, I did. Adam was there over night and nobody else was. First, there was a confrontation. Shortly after that, she was hit on the back of the head four times. She was strangled before she went over the deck. Reporter: Adam's attorney says none of it makes sense. Adam says he never left the guest house that night and none of his DNA or fingerprints were found. His attorney says there is no evidence tying his client to Rebecca's death. The matter of -- A jury is finally hearing the evidence. What is the deft -- It's a civil case, not criminal, but soon there will soon be a verdict. Is Adam responsible? Not one single the witness, we have in testimony that Adam shacknai did any of those things. Reporter: The testimony began Wednesday. This is only about finding the truth that my sister did not commit suicide. The verdict is a month away but no decision will bring little max back to his mother. I will never be as happy as I was when I was with max. Just miss having a life with him. Reporter: For "Nightline," in Coronado, California.

This transcript has been automatically generated and may not be 100% accurate.

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