DALLAS — Texas Attorney General Ken Paxton is already facing calls to resign and accusations of crimes by his own staff over an investigation sought by one of his wealthy donors. Now, the Republican's office is contending with a threat of possible legal action from that donor.

In a letter sent Sunday, a lawyer for Austin real estate developer Nate Paul wrote that Paxton's staff was always hostile to the probe. The letter does not specifically say Paul will sue, but it is styled as a "litigation hold" demanding the preservation of all related documents. It also questions the legitimacy of the announcement last week closing the investigation.

The letter adds to the confusion surrounding investigations and legal disputes that came to public attention this month when seven top lawyers in Paxton's office accused him of bribery, abuse of office and other crimes. The unspecified accusations stem from the attorney general hiring an outside lawyer to look into Paul's claims of wrongdoing by state and federal law enforcement.

Paul's attorney, Michael Wynne, said he learned from media reports late Friday that the investigation was closed.

"We were never contacted by the OAG regarding this apparently pressured decision, and as such question whether this was in fact an accurate and a legitimate communication from your office," Wynne said.

Paxton's office did not respond to a request for comment on the letter. Wynne released it to reporters Sunday night but has not said if Paul will actually sue.

The attorney general's office announced Friday that the investigation was closed after prosecutors in Austin expressed unease. Paxton has denied wrongdoing and cast blame on "rogue employees and their false allegations."

Paul donated $25,000 to Paxton's 2018 reelection campaign but the exact nature of their relationship is unclear. The specifics of Paul's allegations are likewise unknown. The FBI, which searched Paul's home and office last year, declined to comment.

The attorney general's staff has raised concerns that Paxton used his office to benefit Paul. At least one subpoena issued in the case went to a business in conflict with the developer, but Wynne called the claim "preposterous."

Wynne said Paul "met with open hostility" when he sat down with Paxton's staff in July. The director of law enforcement "berated and insulted my client," the lawyer wrote, driving enmity that eventually led Paxton to hire an outside attorney, Brandon Cammack.

Cammack, a 2015 law school graduate and criminal defense attorney, said Paxton reached out to him in August about investigating violations of state law. He said a former federal prosecutor and other candidates also interviewed for the job.

"When he asked me to come out and do justice and stand behind finding out the truth underlying the complaint, you take that seriously and you rise to the occasion," Cammack said.

Cammack said he knows Wynne through legal and civic organizations in Houston. He emphasized they are not close but said the connection may have led Paxton to consider him.

"My name got dropped in the hat, along with other attorneys. Michael may have done that," Cammack said. Wynne has not responded to questions about his role in the hiring.

Paxton is also facing criminal charges in a securities fraud case that has stalled since he pleaded not guilty in 2015. In a court filing made public Monday, the special prosecutors in that case questioned his office paying Cammack $300 an hour. A onetime donor to Paxton sued over the prosecutors getting the same rate, calling it exorbitant and unfair to taxpayers.

Cammack said he's yet to be paid.

Wynne's letter came days after a Texas judge sanctioned him in a legal dispute involving Paul, an Austin nonprofit with a financial stake in the developer's business, and the attorney general's office.

Travis County Judge Jan Soifer on Friday ordered Wynne to personally pay financial penalties for acting in "bad faith" in a suit the Roy F. and Joann Cole Mitte Foundation brought against Paul's companies. The judge said Wynne sued on behalf of shell companies controlled by Paul and created to intervene in the case.

Wynne called this "blatantly inaccurate," said the "lawsuit was brought entirely in good faith" and vowed to appeal.