Chats from a private Telegram group obtained by ProPublica show how a suspect tied to the Jan. 6 insurrection tried to organize a self-styled militia. The hidden proliferation of such groups worries experts.

New video, found in an archive of data uploaded to Parler, includes a fresh look at the mob’s confrontation with Eugene Goodman, the officer credited for luring rioters away from senators during the early moments of the Capitol riot.