Lawmakers need to know how security in Washington D.C. collapsed in the face of a “mad, angry mob,” the chair of the Senate Rules Committee said.

Congress is set to hear Tuesday from former security officials about the events on Jan. 6, when protestors stormed the Capitol building. Supporters of then-President Donald Trump marched on the federal building as lawmakers were certifying the results of the Nov. 3 election. Five people, including police officer Brian Sicknick, died as a result of the melee.

Sen. Amy Klobuchar, D-Minn., the chairwoman of the Senate Rules Committee, told The Associated Press that lawmakers need to figure out how security lapsed in the face of “a mad, angry mob invading this temple of our democracy.”

Klobuchar said lawmakers want answers on what seemed to be a delayed response from the National Guard, the chain of command among top security brass, and how the various agencies responding to the unrest shared information, if any, ahead of the unrest.

“We are on a fast track here simply because decisions have to be made about the Capitol,” she said.

Among those testifying before a joint panel of the Senate Homeland Security and Governmental Affairs Committee and the Senate Rules Committee are former Senate Sergeant-at-Arms Michael Stenger, former House Sergeant-at-Arms Paul Irving, former Capitol Police Chief Steven Sund, and the acting chief of police for the Metropolitan Police Department Robert Contee.

Many of those officials resigned in the wake of the Jan. 6 unrest.

Senate Homeland Security Chairman Gary Peters, D.-Mich., told Politico he had a “long list of questions” about the events on Jan. 6. He added that the Tuesday hearings may be the first of many looking into the events.

Politico’s reporting finds lawmakers will be focused on whether political considerations led to any delay in the security response and how House Speaker Nancy Pelosi and then-Senate Majority Leader Mitch McConnell dealt with any lapses.

“The failure of the nation’s law enforcement apparatus to fully understand the gravity of the situation coupled with the president’s dramatic and deliberate incitement to violence led to the failure of any and all plans previously briefed to the Congress,” Drew Hammill, an aide to the House speaker, said in a statement.

The investigation has led to hundreds of arrests already. Several police officers across five departments are under investigation for participating. 

Trump was charged in the House with one count of impeachment for inciting an insurrection. He was acquitted in the Senate, though a handful of Republicans crossed party lines to vote in favor of conviction.

capitol riots More than 180 people have been charged by federal prosecutors so far over the Jan. 6, 2021, attack on the U.S. Capitol by supporters of then-president Donald Trump. Photo: AFP / ROBERTO SCHMIDT