The FBI warned ominously Monday of potential armed protests by Trump supporters ahead of Biden's inauguration.
The statement was accompanied by an image of a masked suspect wearing gloves and a hooded sweatshirt, carrying an object.
The U.S. Capitol Police said Officer Brian D. Sicknick was injured "while physically engaging with protesters" during the Wednesday riot, later dying in hospital.
The riot undercut the image Washington has long projected as a champion of democracy despite its past interference in the politics of other nations, experts said.
Education Secretary Betsy DeVos and Transportation Secretary Elaine Chao are among the growing list of officials who are abandoning Trump after his supporters stormed the Capitol.
Just blocks from the White House, protesters -- many without masks -- gathered in Freedom Plaza to decry the vote in the Electoral College.
Trump's supporters are planning to rally Tuesday and Wednesday, seeking to bolster the president's unproven claims of widespread voter fraud.