When Mary says she learned her sister, Rebecca Zahau, was found dead, hanging naked from a balcony at her boyfriend’s California mansion, she knew that something was amiss. She insists that even though police did a seven-week investigation and concluded that Zahau died by suicide, her sister would never end her own life.

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Mary and her family claim that Zahau was murdered by her boyfriend’s brother, Adam Shacknai, who found Zahau’s body and claimed he tried to revive her with CPR.

WATCH: What Rebecca Zahau’s Family Claims Happened To Her The Day She Died 

In the video above from Tuesday’s episode of Dr. Phil, hear the 911 call Shacknai placed the day Zahau’s body was found. Why does Mary claim it proves Shacknai is lying? This exclusive interview airs Tuesday. Watch more here.

Adam Shacknai maintains that he is innocent of any wrongdoing and did not kill Rebecca Zahau.

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Why Forensic Pathologist Says Investigation Into Rebecca Zahau’s Death Needs To Be Re-Opened