The Capitol Hill police officer who fatally shot pro-Trump extremist Ashli Babbitt while defending the US Capitol on January 6 has been cleared.

Citing a police memo, NBC News reports the unidentified officer was fully exonerated by an internal investigation, months after the Justice Department said in April it would not press charges.

Video shows Babbitt, wearing a Donald Trump flag as a cape, attempting to climb through the broken window of a door where elected officials were being led away from a far right mob attempting to stop the certification of the 2020 election.

“As members of the mob continued to strike the glass doors, Ms. Babbitt attempted to climb through one of the doors where glass was broken out,” the Department of Justice (DOJ) reported.

“An officer inside the Speaker’s Lobby fired one round from his service pistol, striking Ms. Babbitt in the left shoulder, causing her to fall back from the doorway and onto the floor.”

Thousands of protesters had gathered on Capitol Hill, many calling for the capture or execution of Vice President Mike Pence, whom they thought could stop Joe Biden from becoming the 46th president.

Babbitt was an Air Force veteran who had become a supporter of the cultish QAnon conspiracy collective that believes Trump will be reinstated as president, despite having lost the election by more than 7 million votes.

Whipped up by Trump

The uprising at the Capitol began with a “Stop the Steal” rally, where Trump further pushed claims of election fraud.

Babbitt’s death has become a rallying cry for far-right extremists who have come to see her as a martyr and demand the name of the officer responsible for shooting her.

Trump, who campaigned as a “law and order” candidate, indicated last month that officer should be singled out.

“Who shot Ashli Babbitt?” Trump asked.

“People want to know and why.”

The 35-year-old San Diego woman’s husband filed a lawsuit requesting the identity of the cop who killed Babbitt.

A lawyer representing the officer called his client’s actions “nothing short of heroic”.

Arizona Republican Representative Paul Gosar has referred to the shooting as “an execution”.

-AAP