The individual who filed a whistleblower complaint with the intelligence community’s inspector general last month is a CIA officer who was at one point detailed to the White House, The New York Times reported Thursday citing three unnamed people familiar with his identity.

The whistleblower has since returned to the CIA, the paper reported.

The complaint focused on events surrounding a call between Trump and Ukraine’s president Volodymyr Zelensky, during which Trump pressured Zelensky to investigate Joe and Hunter Biden. The complaint alleged that the White House subsequently sought to suppress records of the call, and has prompted the House to launch an impeachment inquiry into Trump.

Little else is known of the whistleblower’s identity, the Times reported.

Trump has relentlessly attacked the anonymous complainant for his actions, reportedly telling a roomful of diplomats on Thursday that the whistleblower was “a spy” and adding that “in the old days, when we were smart with spies and treason, right? We used to handle it a little different than we do now.”

Andrew Bakaj, a lawyer for the whistleblower, refused to confirm the Times’ reporting and told the paper: “Any decision to report any perceived identifying information of the whistle-blower is deeply concerning and reckless, as it can place the individual in harm’s way. The whistle-blower has a right to anonymity.”