Two firefighters loaned to Washington for the day were the only medics on the Capitol steps Jan. 6, trying to triage injured officers as they watched the angry mob swell and attack police working to protect Congress.

Law enforcement agents were "being pulled into the crowd and trampled, assaulted with scaffolding materials, and/or bear maced by protesters," wrote Arlington County firefighter Taylor Blunt in an after-action memo. Some couldn't walk, and had to be dragged to safety.

Even the attackers sought medical help, and Blunt and his colleague Nathan Waterfall treated those who were passin...