Capitol Police Chief Steven Sund said Thursday that he will resign later this month after his police force failed to contain mobs who tried to prevent Congress from ratifying President-elect Joe Biden‘s victory.

His resignation letter came hours after Speaker Nancy Pelosi (D-Calif.) called for him to step down.

Sund will have only been on the job for about seven months when he resigns effective Jan. 16. He made no mention in the letter of Wednesday’s riots in the Capitol, but noted he will transition into a “sick leave status” starting Jan. 17 until he uses up his available sick leave balance of about 440 hours.

“It has been a pleasure and true honor to serve the United States Capitol Police Board and the Congressional community alongside the men and women of the United States Capitol Police,” Sund wrote to the other members of the Capitol Police Board.

Other members of the Capitol Police Board are also resigning or are under pressure to follow suit.

Pelosi announced Thursday that the House sergeant at arms, Paul Irving, had tendered his resignation. Senate Minority Leader Charles Schumer (D-N.Y.) also said Thursday that he would fire the Senate sergeant-at-arms, Michael Stenger, when Democrats take over the majority later this month.

Irving has served in his role since 2012.

“I think we have to have a full review,” Pelosi told reporters in the Capitol earlier Thursday. “What was underestimated? That the president of the United States would not be as inciteful? Perhaps somebody thought for a moment that he would be patriotic before he leaves office for just this once.

A 35-year-old woman participating in the violent riots was shot by a Capitol Police officer as she tried to force her way toward the House chamber. Glass panels adorning the Speaker’s Lobby — where she was trying to enter — are now cracked and broken due to the mob.

Sund said in a statement Thursday that the officer involved has been placed on administrative leave and is under investigation.

Sund also said that more than 50 Capitol Police and Metropolitan Police officers were injured, including several who were hospitalized with serious injuries.

Most of the insurrectionists were not wearing masks despite the COVID-19 pandemic and attacked police officers with metal pipes and chemical irritants.

The Capitol Police said earlier this week that it would have additional personnel on duty Wednesday in anticipation of demonstrations over Congress meeting in a joint session to formally certify the Electoral College votes.

But the Capitol Police were vastly overwhelmed by the raging mob. The D.C., Virginia and Maryland National Guard and state troopers were all called in to help contain the terror attack and it took about four hours to clear the Capitol complex.

Sund said in the earlier statement Thursday that the Capitol Police is conducting a “thorough review” of Wednesday’s security planning and procedures but defended his force’s actions.

“Maintaining public safety in an open environment – specifically for First Amendment activities – has long been a challenge. The USCP had a robust plan established to address anticipated First Amendment activities. But make no mistake – these mass riots were not First Amendment activities; they were criminal riotous behavior. The actions of the USCP officers were heroic given the situation they faced, and I continue to have tremendous respect in the professionalism and dedication of the women and men of the United States Capitol Police,” Sund said.

Rep. Zoe Lofgren (D-Calif.), who chairs the House Administration Committee, said that she had been misled about the state of preparedness in a briefing with Sund and House Sergeant at Arms Paul Irving earlier in the week.

“We were told that was all in place and there was no doubt completely able to keep us secure in the Capitol,”  she said, specifying that she had been told that the coordination with the National Guard was ready to go.

“Well that was not correct. Not only were they not prepared, what they told me about the National Guard was just not true. The guard was not even activated,” she said.

Lofgren also indicated that President Trump was slow to react to requests to mobilize the National Guard, an issue that normally falls to governors, but rests on the commander-in-chief when it comes to the District of Columbia.

A call from Congress’s bipartisan leaders, she said, was necessary to get the Defense Department to mobilize the National Guard.