On social media sites requested by the far-right, such as Gab and Parler, directions on which streets to take to avoid the police and which tools to bring to help pry open doors were exchanged in comments. At least a dozen people posted about carrying guns into the halls of Congress…

On Gab, they documented going into the offices of members of Congress, including that of House Speaker Nancy Pelosi. Dozens posted about searching for Vice President Mike Pence, who had been the target of Mr. Trump’s ire earlier in the day.

At 2:24 p.m., after Mr. Trump tweeted that Mr. Pence “didn’t have the courage to do what should have been done,” dozens of messages on Gab called for those inside the Capitol building to hunt down the vice president. In videos uploaded to the channel, protesters could be heard chanting “Where is Pence?”