This is an archived article and the information in the article may be outdated. Please look at the time stamp on the story to see when it was last updated.

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. 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.

The breach halted the effort by Congress to certify President-elect Joe Biden’s victory. Protesters stormed the building and occupied it for hours. The lawmakers eventually returned and finished their work.

In his first public comment on the mayhem from Wednesday, Sund said in a statement that rioters “actively attacked” Capitol police and other law enforcement officers with metal pipes, discharged chemical irritants and “took up other weapons against our officers.”

Lawmakers from both parties have pledged to investigate law enforcement’s actions and questioned whether a lack of preparedness allowed a mob to occupy and vandalize the building.

Mayor Muriel Bowser joined in the criticism of the police response. “Obviously it was a failure or you would not have had people enter the Capitol by breaking windows and terrorizing the members of Congress who were doing a very sacred requirement of their jobs.”