The new witness in the Coronado mansion deaths -- who is claiming they heard a "scream for help" hours before cops said Rebecca Zahau died -- attempted to report the information to police twice but was "blown off," RadarOnline.com has exclusively learned.

As we previously revealed, the informant, whose identity has not been released, contacted Zahau's anguished family on Wednesday and provided them with sensational information that could blow the suicide theory to pieces.

According to the witness, they heard screams from inside the Coronado, Calif., mansion at 11 p.m.

The family of Rebecca Zahau isn't giving up its quest to have the mysterious mansions death case re-investigated, despite the California Attorney General denying a similar request by the woman's pharmaceutical tycoon boyfriend to take another look at the supposed suicide hanging and coincidental fatal fall of his son.

The Zahaus are challenging the San Diego County Sheriff's Department's finding that Rebecca, 32, killed herself by binding her wrists and ankles and hanging herself naked from a balcony at Jonah Shacknai's historic mansion in Coronado, California.

As RadarOnline.com revealed, the family's high-powered lawyer Anne Bremner sent an email to California Attorney General Kamala D. Harris on Wednesday requesting a full and independent investigation because she had obtained "compelling evidence to be investigated" and "new critical witnesses to be interviewed."

There appears to be yet another mystery in the Rebecca Zahau death case, involving an unknown set of footprints on the balcony that cops claimed Rebecca jumped to her death from, RadarOnline.com is exclusively reporting. Rebecca's family refuses to accept that she killed herself, and have asked authorities to re-open the case.

Rebecca’s naked body was found hanging from the balcony at her billionaire boyfriend Jonah Shacknai's mansion in Coronado, CA. (a suburb of San Diego), two days after his son, Max, 6, was found unconscious at the base of the stairs. Max later died from his injuries.