U.S. Capitol Police Chief Steven Sund is resigning amid criticism over an apparent lack of preparedness to deal with Wednesday's violent mob on Capitol Hill.

Sund's resignation is effective January 16, according to a Capitol Police official.

House Speaker Nancy Pelosi on Thursday called for the resignation of the Sund and said the House Sergeant at Arms has told her he is submitting his resignation as well.

Pelosi made her comments during her weekly news conference, and follows Senate Democratic Leader Chuck Schumer saying he would fire the current Senate Sergeant-at-Arms when he becomes majority leader.

"If Senate Sergeant Arms Stenger hasn't vacated the position by then, I will fire him as soon as Democrats have a majority in the Senate," Schumer said in a statement.

Michael C. Stenger was appointed by Senate Majority Leader Mitch McConnell and it was expected that Schumer would eventually replace him when the chamber flipped to Democrats. But Schumer is making clear Stenger either needs to resign or be fired in the wake of the events that transpired, part of the growing reaction to the mob that stormed Capitol Hill.

Earlier Thursday, Capitol Police leadership provided first details about the deadly incident that left lawmakers and staff fearful for their lives.

In a statement released Thursday morning, Sund detailed the violent actions of the rioters saying that Capitol Police and other law enforcement officers were "actively attacked" with metal pipes and other weapons.

"They were determined to enter into the Capitol Building by causing great damage," Sund said.

The Capitol Police fired on an adult female as "protesters were forcing their way toward the House Chamber where Members of Congress were sheltering in place." The woman was later pronounced dead after being transported to a nearby hospital. The officer involved has been put on administrative leave pending a joint investigation with Capitol Police and the Metropolitan Police Department.

Sund also said Capitol Police responded to reports of pipe bombs and a suspicious vehicle on the southeast corner of the Capitol, adding that the Capitol police "determined that both devices were, in fact, hazardous and could cause great harm to public safety."

The FBI is investigating the incident further.

The Capitol Police revealed for the first time that 13 people have been arrested for "unlawful entry" of the capitol complex, in addition to the owner of the suspicious vehicle. The police said that additional charges may be filed pending further investigation.