Federal prosecutors have charged more than 300 people with taking part in the Jan. 6 riot at the U.S. Capitol, the Department of Justice said Friday, and at least 280 of them have been arrested.
"The investigation into those responsible is moving at a speed and scale that's unprecedented, and rightly so. Those responsible must be held to account, and they will be," acting Deputy Attorney General John Carlin said.
On Thursday, acting U.S. Capitol Police Chief Yogananda Pittman told Congress of her concern that members of some of the same groups involved in last month's riot -- who said they wanted to attack the Capitol and even kill members of Congress -- might try to target President Joe Biden's first message to a joint session.
Asked about the potential threat Friday, a senior FBI official said investigators have been watching extremist groups carefully since the election. "We are watching very closely for any reaction from individuals that would show either intent to commit an attack or somebody that has already committed one," the official said.
No date has been set yet for the Biden speech.
Justice Department officials say they've expanded the number of lawyers and investigators devoted to cases of domestic terrorism. Anti-government sentiment and racial or ethnic hatred are now the top two motivations for attacks by domestic violent extremists, the official said.
"2020 was a busy year. The violent reaction to a mixture of events that took place around the country is unlike anything we have seen in decades."
Carlin said investigations must be based on the potential violation of a law, never on someone's First Amendment beliefs or associations.
Success in these cases "is not the prosecution of a violent extremist or terrorist after the fact, when families have lost loved ones or are grieving. Success is the disruption before violence occurs," he said.