Pressure on Trump Intensifies as Resignations Roil End of His Term

With less than two weeks before President-elect Joseph R. Biden Jr. takes the oath of office, it seemed on Thursday that the wheels might finally be coming off the Trump administration.

In 24 hours, Congress reconvened in a Capitol breached and battered by a pro-Trump mob, formalized Mr. Biden’s victory over the objections of more than 100 Republican lawmakers and found itself on the brink of impeaching President Trump a second time.

A growing cohort of legislators, including at least one Republican, expressed support for stripping Mr. Trump of his powers under the 25th Amendment, even as Vice President Mike Pence — who would have to lead that process — was said to oppose the idea.

On Capitol Hill, the number of Republicans willing to publicly defend Mr. Trump dwindled. One, Representative Adam Kinzinger of Illinois, said he supported the invocation of the 25th Amendment; another, Representative Steve Stivers of Ohio, said he “would not oppose” the move if cabinet members decided to proceed.

Several high-ranking administration officials announced that they would resign including two cabinet members, a late and purely symbolic gesture by people who had stood by Mr. Trump even as he promoted baseless claims of election fraud and repeatedly refused to accept his loss.

Kayleigh McEnany, the White House press secretary, claimed that “the entire White House” abhorred the violence that Mr. Trump himself had incited, then walked off without answering any questions. She spoke for two minutes in the White House press briefing room and did not mention the president by name, or his speech that set the violence at the Capitol in motion.

All of this unfolded amid the strange silence of a Trump-free Twitter, with the president’s account temporarily locked after he tweeted praise for the mob that had ransacked the Capitol, leading to at least four deaths.

Mr. Trump returned to Twitter late on Thursday after his suspension lifted and he posted a two-minute video that addressed the violence and acknowledged that “a new administration” would be sworn in on Jan. 20.

Maggie Haberman contributed reporting.

A United States Capitol Police officer died Thursday night from injuries sustained when he engaged with a pro-Trump mob that descended on the U.S. Capitol the day before.

Officer Brian D. Sicknick died at about 9:30 p.m. on Thursday, the Capitol Police said in a statement. He had been with the agency since 2008.

Mr. Sicknick was responding to the riots on Wednesday and “was injured while physically engaging with protesters,” the agency’s statement said, although officials didn’t immediately elaborate on the nature of his injuries or how he interacted with the crowd. After sustaining the injuries, Mr. Sicknick returned to his division office, collapsed, and was taken to the hospital.

“The entire U.S.C.P. department expresses its deepest sympathies to Officer Sicknick’s family and friends on their loss, and mourns the loss of a friend and colleague,” the statement said. News outlets had prematurely reported on his death earlier in the day while he was apparently still on life support.

Homicide investigators from the Metropolitan Police Department are involved in the case.

Early Friday morning, Representative Tim Ryan of Ohio, a Democrat who runs the House Appropriations subcommittee that oversees the budget for the Capitol Police, said in a Twitter post that his heart was breaking over Mr. Sicknick’s death.

“This tragic loss is a reminder of the bravery of the law enforcement who protect us every day,” Mr. Ryan wrote.

Mr. Sicknick’s death brings the death toll from Wednesday’s mayhem to five. One of the people participating in the pro-Trump rampage, Ashli Babbitt, was shot and killed by a Capitol Police officer inside the building as she climbed through a broken window leading to the Speaker’s Lobby. Three other people died after experiencing apparent medical emergencies in the area around the Capitol, the police said.

Officials have said that some 50 police officers were injured as the mob swarmed barricades, threw objects, battered doors, smashed windows and overwhelmed some of the officers who tried to resist the advancing crowd.

Capitol Police reported 14 arrests during the incursion, including two people who were detained for assaulting a police officer. Local police arrested dozens of others, mostly for unlawful entry and violations of the city’s Wednesday night curfew.

Steven Sund, the Capitol Police chief, handed in his resignation on Thursday after facing pressure from congressional leaders. The sergeants-at-arms of the House and Senate also resigned.