WASHINGTON — U.S. Capitol Police officers who were attacked and beaten during the Capitol riot filed a lawsuit Thursday against former President Trump, his allies and members of far-right extremist groups, accusing them of intentionally sending a violent mob on Jan. 6 to disrupt the congressional certification of the election.

The suit in federal court in Washington alleges Trump “worked with white supremacists, violent extremist groups, and campaign supporters to violate the Ku Klux Klan Act, and commit acts of domestic terrorism in an unlawful effort to stay in power.”

The suit was filed on behalf of the seven officers by the Lawyers’ Committee for Civil Rights Under Law. It names the former president, the Trump campaign, Trump ally Roger Stone and members of the extremist groups the Proud Boys and Oath Keepers who were present at the Capitol and in Washington on Jan. 6.

Two other similar cases have been filed in recent months by Democratic members of Congress. The suits allege the actions of Trump and his allies led to the violence siege of the Capitol that injured dozens of police officers, halted the certification of Democrat Joe Biden’s electoral victory and sent lawmakers running for their lives as rioters stormed into the seat of American democracy wielding bats, poles and other weapons.

Violent protesters loyal to President Trump storm the Capitol in Washington on Jan. 6. John Minchillo/Associated Press

A House committee has started in earnest to investigate what happened that day, sending out requests Wednesday for documents from intelligence, law enforcement and other government agencies. Their largest request so far was made to the National Archive for information on Trump and his former team.

Trump accused the committee of violating “long-standing legal principles of privilege,” but his team had no immediate comment on Thursday’s lawsuit.

“Executive privilege will be defended, not just on behalf of my Administration and the Patriots who worked beside me, but on behalf of the Office of the President of the United States and the future of our Nation,” Trump said in a written statement.

Also Thursday, a Capitol Police officer who fatally shot an unarmed Trump protester told “NBC Nightly News” in an interview that he had no other choice but to shoot.

“I tried to wait as long as I could,” Lt. Michael Byrd said. “I hoped and prayed no one tried to enter through those doors. But their failure to comply required me to take the appropriate action to save the lives of members of Congress and myself and my fellow officers.”

He was cleared of any wrongdoing in the shooting of Ashli Babbitt, 35. His name had been withheld by authorities over safety concerns, but he came forward publicly on NBC. Byrd said they were trapped, barricaded inside with lawmakers he was sworn to protect. He heard the mob coming and his anxiety worsened. He said he yelled repeatedly for the rioters to get back.

On the other side of the door, video showed the moment he fired the single shot, after rioters screamed at police to get out of the way and broke through the glass door leading to the doors of the House chamber. Byrd fired one shot, striking Babbitt as she was trying to climb through the jagged opening in the window. She was unarmed.

“I know that day I saved countless lives,” Byrd said. “I know members of Congress, as well as my fellow officers and staff, were in jeopardy and in serious danger. And that’s my job.”

At least 140 officers were injured. The lawsuit names as defendants several people who have been charged with federal crimes related to the riot. They are alleged to have “conspired to use force, intimidation, and threats to prevent Joe Biden and Kamala Harris from taking office, to prevent Congress from counting the electoral votes, and to prevent the Capitol Police from carrying out their lawful duties.”

The filing provides vivid accounts of the injuries the officers sustained while trying to fend off the mob as rioters pushed past lines of overwhelmed law enforcers and barged into the Capitol. One officer, Jason DeRoche, was hit with batteries and sprayed with mace and bear spray until his eyes were swollen shut. A second officer, Governor Latson, was inside the Senate chamber when the rioters broke through the doors and beat him as they shouted racial slurs, according to the suit.

“We joined the Capitol Police to uphold the law and protect the Capitol community,” the group of officers said in a statement released by their lawyers. “On Jan. 6 we tried to stop people from breaking the law and destroying our democracy. Since then our jobs and those of our colleagues have become infinitely more dangerous. We want to do what we can to make sure the people who did this are held accountable and that no one can do this again.”

The documents requested by the House committee this week are just the beginning of what is expected to be a lengthy, partisan and rancorous congressional investigation into how the mob was able to infiltrate the Capitol and disrupt the certification of Democrat Joe Biden’s presidential victory, inflicting the most serious assault on Congress in two centuries.

Committee members are also considering asking telecommunications companies to preserve phone records of several people, including members of Congress, to try to determine who knew what about the unfolding riot and when they knew it. With chants of “hang Mike Pence,” the rioters sent the then-vice president and members of Congress running for their lives and did more than $1 million in damage, and wounded dozens of police officers.

The demands were made for White House records from the National Archives, along with material from the departments of Defense, Justice, Homeland Security and Interior, as well as the FBI and the Office of the Director of National Intelligence.

The committee so far has heard from police officers who were at the Capitol on Jan. 6. In emotional testimony, those officers spoke of how afraid and frustrated they were by the failure of law enforcement leaders to foresee the potential for violence and understand the scope of planning by the Trump backers.

AP Congressional Correspondent Lisa Mascaro contributed to this report.