Updated

At least one U.S. senator called for an investigation into the police response after Trump supporters gained access to the U.S. Capitol on Wednesday, forcing the complex to lock down and Congress into a recess while crowds waving American, Confederate and pro-Trump flags descended on the steps outside the building. 

Speaking with reporters on the Hill, Sen. Roy Blunt, a Republican from Missouri, called on the U.S. Capitol Police to conduct a swift internal review of what unfolded Wednesday in order to identify and correct any mistakes made before the presidential inauguration on Jan. 20.

"I think the Capitol Police will and should really do a quick review here of what went wrong and what they need to do to be sure nothing like that could happen again," Blunt said. "It will be interesting to see what they determine either both through their intelligence information, or just a failure to really realize the threat potential."

He added: "You want to take one more really hard look at what you thought your crowd security concerns might be for."

CAPITOL HILL VIOLENCE SPARKS UNREST OUTSIDE TRUMP PROPERTIES

In its first public statement since the incident, U.S. Capitol Police said Thursday that its officers and law enforcement partners "responded valiantly when faced with thousands of individuals involved in violent riotous actions as they stormed the United States Capitol Building."

"These individuals actively attacked United States Capitol Police Officers and other uniformed law enforcement officers with metal pipes, discharged chemical irritants, and took up other weapons against our officers. They were determined to enter into the Capitol Building by causing great damage," the agency said. 

Capitol Hill Police Chief Steven Sund confirmed that the department "is conducting a thorough review of this incident, security planning and policies and procedures."

"The violent attack on the U.S. Capitol was unlike any I have ever experienced in my 30 years in law enforcement here in Washington, D.C. Maintaining public safety in an open environment – specifically for First Amendment activities – has long been a challenge," Sund said. "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," he added. 

Thousands of people began lining up before sunrise Wednesday to see President Trump address a crowd gathered at the Ellipse at 11 a.m. The "Save America Rally" was a federally permitted event and happened hours before a crowd would eventually breach the U.S. Capitol and interrupt the democratic process of formally certifying the Electoral College votes.

Video circulated online purportedly showed U.S. Capitol Police officers removing metal barricades blocking access to the U.S. Capitol complex. A crowd of people, many of whom waved pro-Trump, American and Confederate flags, then appeared to finish the job, shouting and tearing down the gates.

U.S. Capitol Police has not returned a Fox News request for comment about the video Thursday.

The FBI on Thursday renewed its call for help in identifying "individuals instigating violence in Washington, D.C." The agency is accepting tips and digital media "depicting rioting or violence in and around the U.S. Capitol on January 6."

Anyone with information on those photographed inside the U.S. Capitol is asked to call 1-800-CALL-FBI (1-800-225-5324) or visit http://fbi.gov/USCapitol.

NATIONAL GUARD DEPLOYED TO CAPITOL BUILDING AMID PROTESTS, UNREST

Additional videos showed several lines of fencing knocked down by protesters before they approached the building. Footage also showed a line of officers, wearing helmets and holding shields, attempt to push back the crowd before people reached the steps of the Capitol.

Both chambers of Congress went into recess around 2 p.m. Wednesday, and the U.S. Capitol was placed under lockdown after a group breached the fences outsides, and an undisclosed number gained entry into the building. At the time, just 12 Electoral College votes had been counted and lawmakers had been debating the results for Arizona. An announcement played instructing people to shelter in place.

Once inside the building, video showed officers using batons to try to hold back crowds flowing into the lobby. Tear gas was also deployed, but the large group overwhelmed officers. Photos and videos of inside the House chamber showed U.S. Capitol Police officers with their guns drawn pointed toward a window smashed by people crowded outside the room. People gained access to the Senate chamber, and another photo showed a man hanging from the balcony.  

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One woman, identified as a veteran from San Diego, was shot inside the building and was transported to the hospital. She was later declared dead. It is unclear if it happened inside the Capitol, but police said three other people died in the unrest from medical emergencies.

More than 70 people were arrested.