INSIDE EDITION Speaks to Mother of Son in Mansion Mystery

INSIDE EDITION exclusive! The mother of the 6-year-old boy who mysteriously died while in the care of his millionaire father's girlfriend speaks for the first time about why she thinks it may have been murder.  

Dina Shacknai is talking about her six-year-old son Max, who was killed in a bizarre and mysterious double tragedy at her millionaire ex-husband's oceanfront mansion.

"They need to reopen the case and investigate and find out what happened to Max," said Dina.
Now, Dina is making a new and stunning claim: Max was murdered.

Max Shacknai was killed in a fall from a second floor landing at his dad's home in San Diego. Police say it was an accident.  

"I don't understand why this was determined to be an accident when the conclusions did not match his injuries or the findings at the scene," said Dina.

Two days later, his father's beautiful 32-year-old girlfriend, Rebecca Zahau, was found hanged from a balcony at the mansion, naked, and with her hands bound behind her back.

Police ruled her death a suicide, and even released a video showing how she bound her own hands behind her back.

Now, a year after the tragedy, two experts say Max's death was no accident.

"For that to have happened, and to think that he was murdered is horrible, but that's the truth," said Dina.

Dina, who shared custody with her millionaire ex-husband Jonah Shacknai, asked a pathologist and an accident expert to investigate Max's death.

In a just-released report, they say that Max's death was a "homicide."

"Max was assaulted...on the second floor. Then he was lifted over the banister...falling down to the front entryway below," said the report.

The report claims Max's extensive injuries can't be explained any other way.

And the report points a finger at Zahau as the likely killer, especially since she killed herself afterwards.

Zahau's family call that "preposterous."

A family spokesman said: "Rebecca loved Max as if he were her own son."

Dina says Max's tragic death has been devastating.

"There were some nights when he would just say, 'Mom, can we just talk tonight?' And I think that's an amazing thing for a five-year-old boy to say to his mom," said Dina.

A children's charity has been created in Max's name. Its logo was taken from a Mother's Day gift he made for his mom.

"It says Max on one side and mom," said Dina.

Authorities in San Diego staged an elaborate two-hour presentation of their findings on accidental death and suicide last year. They say they're studying the new report.

"The resolution for me in this, is for them to reopen the case and for Max to have justice," said Dina.