FBI acting Director Paul Abbate announced his retirement on Monday, just one day after taking leadership of the bureau from now-former Director Christopher Wray.

Wray stepped down on Sunday and Abbate had been expected to serve in the role until Kash Patel, President Donald Trump's nominee for the job, received Senate confirmation. He had long served in the post of deputy director and was a veteran of the agency. But Abbate abruptly announced his own retirement after one day at the top of the bureau in an email which did not appear to include an explanation.

"When the Director asked me to stay on past my mandatory date for a brief time, I did so to help ensure continuity and the best transition for the FBI. Now, with new leadership inbound, after nearly four years in the deputy role, I am departing the FBI today," he said, according to the Associated Press. “As you move forward, continue to stay true to our core values, be there for our partners, and take care of those who serve alongside you. Thank you for your service."

The bureau's career officials have come under considerable scrutiny from Trump's supporters over widespread accusations of political bias within the agency.

Brian Driscoll will lead the agency until the Senate confirms a permanent replacement, CBS News reported.