The Capitol Police officer, who was killed in the attack, was identified as an 18-year veteran of the force.
He was killed when a 25-year-old man rammed the auto into two officers at a barricade outside the Capitol building on Friday, April 2.
Officer William Evans, an 18-year veteran of the force, was killed after Noah Green, 25, ploughed his vehicle into a security barrier on Capitol Hill on Friday afternoon before leaping out with a knife. He expressed gratitude to the Capitol Police and the National Guard troops for responding quickly to the attack.
"Whether the attack was at law enforcement, or whoever, we have a responsibility to get to the bottom of it and we'll do that", Robert Contee, the acting chief of Washington DC's Metropolitan Police Department, said at a news conference.
When the incident occurred, police alerted staff members: "Due to an external security threat located All U.S. Capitol Campus Buildings, no entry or exit is permitted at this time", the alert reads.
A security review requested by House Speaker Nancy Pelosi, D-Calif., in the aftermath of the riot and conducted by a task force recommended eventually replacing the barrier with mobile fencing and "an integrated, retractable fencing system" that could be used as needed.
U.S. Capitol Police officers stand near a auto that crashed into a barricade on Capitol Hill in Washington, April 2, 2021.
President Joe Biden also ordered that US Flags at the White House be lowered to half-staff until April 6 in honour of a US Capitol Police officer who was killed in the attack. Miriam Carey's family said she suffered from postpartum depression with psychosis but was not risky.
The drama unfolded at a security checkpoint near the Capitol complex, close to where armed insurrectionists stormed the building housing the US Congress on January 6.
Two officers, one from Capitol Police and another from Washington's Metropolitan Police Department, died by suicide following the January 6 attack.
Nearly 140 Capitol Police officers were wounded in that attack, including officers not issued helmets who sustained head injuries and one with cracked ribs, according to the officers' union.
The area was locked down for hours Friday but has since reopened, and National Guard troops stood outside the building on Saturday.
Green's Facebook page, which has since been taken down, included photos and videos of Nation of Islam rallies, and the bio identified Green as a "Follower of Farrakhan".