WASHINGTON — A former senior official in the U.S. Capitol Police accused two of the department’s top officials of failing to properly share vital intelligence in the days ahead of the Jan. 6 insurrection, crippling the response to the attack.

In a blistering letter to Congress, the former official claims that Assistant Capitol Police Chief Yogananda Pittman and acting assistant chief Sean Gallagher received an intelligence report on Dec. 21 that had specific warnings and information about a potential riot similar to a report that the FBI later provided to the department on Jan. 5.

In the 16-page letter, dated Sept. 28, the former official claims that Pittman and Gallagher deliberately never shared this December intelligence report with other department officials or used it to update security assessments provided to Capitol Police officers.

Sharing that information, the former official alleges, could have “changed the paradigm of that day” and “would have provided the documentation needed to support securing the National Guard and other allied agency manpower for January 6th.” It also would have provided the intelligence needed to procure hard gear and other weapons.

A pro-Trump mob stormed the Capitol on Jan. 6 to try to stop the counting of electoral college votes affirming President Joe Biden’s win. In the worst attack on the seat of democracy since the War of 1812, four people died and an officer who had been sprayed with a powerful chemical irritant, Brian D. Sicknick, suffered a stroke and died the following day. Some 140 members of law enforcement were injured as rioters attacked them wielding flagpoles, baseball bats, stun guns, bear spray and pepper spray.

The individual, who sought anonymity for privacy reasons, declined to comment Monday beyond the letter, saying he wants the focus on the allegations he raised. “This is not about me,” the former official said.

In a joint statement responding to the criticism, members of the Capitol Police’s executive team — which includes Pittman and Gallagher along with Chief of Police J. Thomas Manger — said that while “there is more work to do, many of the problems described in the letter have been addressed.”

“The United States Capitol Police has implemented, and continues to implement, many of the critical recommendations called for in a series of post January 6 reviews,” the officials said. “The letter from the former employee echoes the thoughtful recommendations in those reports.”

The former official claims Pittman lied to Congress when she claimed that the critical information detailed in that December report was shared with assistant chiefs and deputy chiefs. The information contained warnings that individuals online were sharing maps of the Capitol campus and were planning on confronting members of Congress while armed. Pittman told Congress that senior officials in the department were aware of these reports, but the former official claims that this is “unconditionally false.”

“It was never sent or shared. It also was never used to update any intelligence brief forwarded to the commanders,” the official writes, claiming that Gallagher and Pittman were the only officials who had “all the intelligence information” on Jan. 6.

A spokesman for the U.S. Capitol Police had no official comment Monday on the accusations.

In a report issued in June, a bipartisan Senate probe found that Capitol Police had specific intelligence that supporters of President Donald Trump were planning on mounting an armed insurrection in the Capitol at least two weeks before the riot — as early as Dec. 21. That probe found that omissions and miscommunication kept that information from reaching officers tasked with defending the building. The joint report by the Senate Rules and Administration and the Homeland Security and Governmental Affairs committees highlights how the intelligence arm of the Capitol Police considered the threat of violence “remote” and “improbable.”

Politico first reported on the letter from the official.

Since the attack, Capitol Police officials have announced changes meant to expand intelligence operations and improve internal communications.

The letter’s author was a Capitol Police leader and left the department soon after the attack. In the letter, the individual writes that he was in the department’s command center with Pittman and Gallagher for part of the attack and described them as “mostly sitting there, blankly looking at the TV screens showing real time footage of the officers and officials fighting for the Congress and their lives.” A law enforcement source, who spoke on the condition of anonymity to talk freely about the day, said the former official was in the command center for a couple of hours.

In the letter, the former official also accuses congressional leaders of “purposefully” failing to tell the truth about the Capitol Police’s failures on Jan. 6 and of failing to hold the two officials accountable.

“The truth may be valued less than politics by many members of the congressional community to include those that have made decisions about the leadership of the USCP post January 6th, but I believe the truth still matters to real people and certainly the men and women of the U.S. Capitol Police,” the former official writes.

The Washington Post’s Aaron C. Davis contributed to this report.