As Ms. Babbitt tried to jump a barrier and enter the speaker’s lobby through a broken window, the Capitol Police lieutenant shot and killed her. While officials have not provided a full accounting of Ms. Babbitt’s fatal encounter, it was caught on video and widely shared on social media.

But footage, combined with witness accounts, seems to show that the lieutenant, who has not been named, was left alone to confront a mob. The lieutenant has been on administrative leave pending the results of the investigation into the shooting and was interviewed by investigators last week…

Lethal force is deemed legally justified if an officer has an “objectively reasonable” fear of serious harm to themselves or others. Two people familiar with the lieutenant’s account suggested that he would argue that he had acted to protect lawmakers from harm. Five people died during the assault on the Capitol and in the immediate aftermath.