WASHINGTON — Acting homeland security secretary Chad Wolf is stepping down, citing recent court challenges to his authority. His move comes nine days ahead of President-elect Joe Biden’s inauguration amid widespread fears about security in the aftermath of a pro-Trump mob’s attack on the Capitol last week.

Wolf announced his resignation Monday, effective at midnight, a decision he said was prompted by several court rulings challenging the validity of his appointment to lead DHS.

Wolf did not specifically cite the storming of U.S. Capitol on Jan. 6, attributing his choice to “recent events.” Wolf was overseas for meetings in the Middle East last week, and DHS has been criticized for failing to prepare for the assault on the Capitol.

“I am saddened to take this step, as it was my intention to serve the Department until the end of this Administration,” Wolf said in a statement. “Unfortunately, this action is warranted by recent events, including the ongoing and meritless court rulings regarding the validity of my authority as Acting Secretary. These events and concerns increasingly serve to divert attention and resources away from the important work of the Department in this critical time of a transition of power.”

Peter T. Gaynor, administrator of the Federal Emergency Management Agency, will take over as acting DHS secretary, Wolf’s statement said.

Wolf has served more than a year in an acting capacity as DHS leader, and the White House withdrew his nomination last week, long after it became clear that the Senate was unlikely to take up a confirmation vote.