Medicis CEO Jonah Shacknai is pictured with Rebecca Zahau in this exclusive picture obtained by ABC News.

A lawyer for pharmaceutical mogul Jonah Shacknai has sent an email to the lawyer representing the family of his dead girlfriend, whose body was found at his historic mansion, threatening to sue if her family’s lawyer doesn’t stop insinuating that Shacknai influenced the probe into her death.

The body of Shacknai’s girlfriend Rebecca Zahau, 32, was found on the grounds of his Spreckels Mansion in Coronado, Calif., July 13. She died two days after Shacknai’s young son fell down the stairs of the mansion, suffering fatal head injuries.

A police investigation determined Zahau’s death was a suicide, but her family has hired lawyer Anne Bremner who has raised questions about the death and has pressed police to reopen the case.

ABCNews.com has obtained an email lawyer Dan K. Webb of the law firm Winston & Strawn LLP sent to Bremner Tuesday morning warning that “your false public statements constitute defamation, per se, and under law, entitle Mr. Shacknai to recover from you, and your law firm, substantial damages.”

“What is most concerning are recent false public statements you have made that Mr. Shacknai, because of his business success, has somehow improperly influenced the investigations… You have further made public comments that these agencies have applied a different standard in conducting their investigations because of Mr. Shacknai’s wealth,” the letter said.

Webb called Bremner’s statements “highly insensitive on a human level. Mr. Shacknai and his family have suffered two tragic losses under the harsh and unkind glare of a national media frenzy you have now helped sustain.”

Bremner responded to the allegations Thursday night, telling ABCNews.com, “I haven’t said anything about his wealth nor have I said anything that could be considered false or defamatory …  We are simply seeking the truth and justice.”

In the email, Webb emphasized that he was not advocating that Bremner’s clients accept the results of the police investigation. “They are, of course, entitled to their point of view regarding this matter,” he wrote.

The email concludes with, “You must cease and desist from making any further false public statements about Mr. Shacknai.”

A spokesman for Shacknai, Terry Fahn, declined to comment.

In July when police arrived at Shacknai’s mansion they found Zahau on the back lawn, her hands tied behind her back and her feet bound. Her body had been cut down by her boyfriend’s brother, Adam Shacknai, who was staying at the home.  A message in black paint on a bedroom near where Zahau was found hanging said, “She saved him can you save her?”

The autopsy report also states there were hemorrhages under Zahau’s scalp, tape residue and blood on her legs, and a T-shirt that was wrapped around Zahau’s neck had been partially stuffed in her mouth.