The head of the U.S. Capitol Police will resign effective Jan. 16 following the breach of the Capitol by a pro-Trump mob.

Chief Steven Sund said Thursday that police had planned for a free speech demonstration and did not expect the violent attack where Trump supporters barged into the building halting the effort by Congress to certify President-elect Joe Biden’s victory. He said it was unlike anything he’d experienced in his 30 years in law enforcement.

He resigned Thursday after House Speaker Nancy Pelosi called on him to step down. His resignation was confirmed to The Associated Press by a person familiar with the matter who was not authorized to speak publicly.