The 35-year-old woman, along with dozens of other supporters of then-President Donald Trump, tried to break open a door to the House of Representatives.
The policeman shot through the door glass and hit the woman in the neck.
His employer, the US Capitol Police, believes the shooting was legal and proper in the circumstances.
Received hot
In a statement, the Capitol Police said that the policeman potentially rescued members of Congress and their staff from a large crowd of insurgents with "serious injury and possible death" as a result.
Trump supporters have been striving to make the woman a martyr.
The ex-president has called the incident a murder.
Since the shooting, the police officer and his family have received credible and detailed threats, according to Capitol Police.
Five lose their lives
Shortly before the storm, Trump encouraged his supporters to stop Congress from formally confirming rival Joe Biden's victory in the November presidential election.
Almost 600 people heeded his call.
Five people, including a police officer, lost their lives in the attack on the Capitol.
More than 500 people have been arrested for involvement in the storm.
So far, only a few have been killed.