Trump supporters try to break through a police barrier, Wednesday, Jan. 6, 2021, at the Capitol in Washington. As Congress prepares to affirm President-elect Joe Biden's victory, thousands of people have gathered to show their support for President Donald Trump and his claims of election fraud. (Photo: AP)

The FBI warned law enforcement agencies ahead of last week's breach of the U.S. Capitol about the potential for extremist-driven violence and prosecutors are now weighing sedition charges against at least some of the Trump loyalists who stormed the building, U.S. officials said Tuesday.

The statements by FBI and Justice Department officials were intended as both a defense of federal law enforcement preparations before the deadly riot and a warning to participants that they are still subject to arrest and felony charges even if they have left Washington.

Misdemeanor counts against some of the dozens arrested so far may still be upgraded to sedition charges that are punishable by up to 20 years in prison and that carry the grave accusation of inciting an effort to overthrow the government, said acting U.S. Attorney Michael Sherwin in Washington.

“This is only the beginning,” he said.

Even for those who have left Washington, “agents from our local field offices will be knocking on your door," said Steven D'Antuono, the assistant director in charge of the FBI's Washington field office in highlighting the nationwide effort to track down participants in the rioting.

The revelations contradict earlier pronouncements from law enforcement leaders about the potential for danger last week. Many, including the former Capitol police chief, said they were unaware of serious concerns and had prepared only for a free speech protest. Capitol police and others didn't immediately respond to questions about the discrepancy.

The press conference came hours after the Washington Post reported on the existence of a January 5 report from the FBI's field office in Norfolk, Virginia, that forecast, in detail, the chances for “war” in Washington the following day. The existence of such a stark warning appeared to contradict the FBI's earlier assertions that it had no specific intelligence that violence could arise.

D'Antuono defended the handling of the information, saying it was shared in 40 minutes with other law enforcement agencies.

Even without intelligence from law enforcement, there had been ample warning about pro-Trump demonstrations in Washington. But U.S. Capitol Police did not bolster staffing and made no preparations for the possibility that the planned protests could escalate into massive, violent riots, according to several people briefed on the law enforcement response. Officials turned down help offered by the Pentagon three days before the riot.

When backup was finally requested, it took more than two hours for troops to mobilize near the Capitol. By then the mob had raged inside for more than four hours.

Once the mob began to move on the Capitol, a police lieutenant issued an order not to use deadly force, which explains why officers outside the building did not draw their weapons as the crowd closed in. Officers are sometimes ordered to keep their weapons holstered to avoid escalating a situation if superiors believe doing so could lead to a stampede or a shootout.

In this instance, it also left officers with little ability to resist the mob. In one video from the scene, an officer puts up his fists to try to push back a crowd pinning him and his colleagues against a door. The crowd jeers, “You are not American!” and one man tries to prod him with the tip of an American flag.

Meanwhile, President Donald Trump on Tuesday took no responsibility for the violent insurrection at the Capitol. He said that his remarks moments before his supporters marched to the Capitol were “totally appropriate.” He made the comments during his first appearance in public since the Capitol siege, which came as lawmakers were tallying Electoral College votes affirming President-elect Joe Biden’s victory.

The rampage through the halls of Congress sent lawmakers of both parties and Trump’s own vice president into hiding, as crowds called for Mike Pence’s lynching for his role overseeing the vote count. The scene also undermined the hallmark of the republic — the peaceful transition of power. At least five people died, including one Capitol Police officer.