Internal reports and emails from the Homeland Security Department show that federal law enforcement authorities were alert to the potential for violence by extremist groups attending a pro-Trump rally in Washington on Jan. 6, which preceded the attack on the Capitol.

A security bulletin, along with other reports on protests, was compiled by the department’s Federal Protective Service (FPS) a day before the attack and warned that anti-government and racially motivated extremists were likely to participate in the rally near the White House and “use the activities as an opportunity to promote their ideologies and motivate followers to promote violence.”

President Donald Trump spoke at the rally and encouraged his followers to march to the Capitol, where lawmakers were meeting to certify electoral college votes confirming Joe Biden’s victory.

The documents, which were obtained by The Washington Post under the Freedom of Information Act, made no predictions about specific violent acts or an attack on the Capitol, and they don’t indicate any response from other law enforcement agencies about what intelligence the government may have possessed ahead of the Jan. 6 attack.

The bulletin indicates that it was shared with other DHS security teams. It’s not clear whether it was provided to the FBI, D.C. police or Capitol Police.

“The lessons learned from the violent and illegal events of January 6th will help enhance our ability to stop future acts of violence,” DHS spokeswoman Sarah Peck said. “DHS is participating in investigations into the response to the attack and internally reviewing how best to enhance information sharing about threats.”

Peck added that “addressing domestic violent extremism is a top priority” for the department. But, citing the continuing investigation into the Capitol attack, she did not comment further on the documents and what may have been shared with other law enforcement organizations.

But the documents do show a level of awareness of potential threats on the part of the FPS, which is responsible for protecting federal properties, including some buildings around the Capitol. At the time of the attack, the agency was coming off months of protests in Washington and Portland, Ore., where protesters had staged nightly, sometimes violent rallies outside a federal courthouse.

In May, an FPS contractor was killed in a shooting outside a federal building in Oakland, Calif. The accused gunman has been linked to the extremist “boogaloo” movement.

FPS officers are accustomed to flagging the presence of extremists and other potentially violent actors at protests and rallies.

The bulletin lists the Internet addresses for more than 30 Facebook groups that the FPS appeared to be aware of, from “March on Congress” to “Trumps MAGA Rally Stop the Steal” to “Fight for Trump Washington DC — 01/06/2021.”

Other Facebook groups were specific to convoys of buses being organized from New Jersey and Ohio. The bulletin shows that the FPS calculated the number of “committed” attendees from each Facebook group and a larger number of people who were “interested” in the events of Jan. 6.

Combined with a second list of Facebook groups in another email, the documents reveal that agents were drawing on information from nearly three dozen social media forums, most ostensibly organized by Trump supporters

Some of the pages were private or locked and could not be accessed Tuesday by The Post.

A Jan. 5 bulletin, approved by the chief of the investigations branch of the Federal Protective Service, focused on the “First Amendment Protected” events leading up to and during Jan. 6.

The distribution list for the memo shows that it was intended for Department of Homeland Security safety managers and protective service officers, as well as law enforcement in the national capital region.

The bulletin stated that the assessment was based on the “best information available” to the agency at the time and was intended for “situational awareness and operational planning to assure the safety and security of the participants, public, federal assets, missions, facilities and occupants.”

While lacking in specific details, the memo discussed possible violence and said extremist groups were “likely” to attend events in D.C. the following day.

The information compiled by the FPS provided enough advance information about the number of people coming to the rally, including from known extremist groups, to raise questions about whether more analysis and intelligence gathering could have prompted alarms ahead of the rally.

Also on Jan. 5, the FBI’s field office in Norfolk, issued an explicit warning that extremists were preparing to travel to Washington to commit violence and “war.” Had the FBI warning been combined with the FPS information on protesters, it could have raised concern about the potential for serious violence.

As violence erupted at the Capitol, FPS officers took note in emails of clashes between protesters and police. But there is little in the documents to show what actions the FPS took or whether they linked any of the violence to specific groups the agency knew were coming to Washington.

In some instances, the warnings by the FPS were alarming, but it was difficult to know the source of the information or the likelihood of violence.

“The Proud Boys are threatening to shut down the water system in the downtown area, which includes government facilities,” according to an email sent before any reports of violence at the Capitol.

It’s unclear where the threat came from or whether the extremist group made any plans to carry out an attack.

“We take every possible precaution to protect the safety of the water supply and of our distribution network and we work very closely with the District and other partners on information sharing,” D.C. Water spokesman Vincent Morris said in a statement.

The email also shows the scale of threats that law enforcement officers were contending with in the hour before rioters began to break through security barricades at the Capitol.

Authorities estimated the size of the crowd around the White House at 25,000, and because of bag restrictions, people were “hiding bags in bushes” around the building.

The email also described a man in a tree near the Ellipse, south of the White House, who appeared to have a rifle. A subsequent email states that D.C. police responded and took a man into custody near the World War II Memorial “with a rifle.” It’s unclear whether the emails refer to the same person.

Among others, the emails were sent to FPS Director Leonard E. Patterson.

Peter Hermann contributed to this report.