Alerts sent out by police said that people in the Capitol were not allowed to exit the building while the police were responding to the incident, in which the driver got out of the vehicle while appearing to brandish a knife before being shot by authorities.
The slain officer was identified by US Capitol Police as William "Billy" Evans, an 18-year veteran of the force.
A US Capitol police officer was killed and a second injured Friday after a vehicle rammed through security and crashed into a barrier at the Washington complex, forcing it into lockdown less than three months after a mob assault on Congress.
In recent weeks some security around the complex has been loosened, with the number of armed National Guard troops at the Capitol reduced and a security fence that created a broad perimeter around the Capitol complex removed. It's unclear which member of law enforcement shot the suspect.
Photographs from the scene showed the auto had rammed through a black perimeter fence erected as a security measure after the attack on the Capitol on January 6, 2021. "At least one officer drew their weapon and shot the suspect".
In the 6 January attack, hundreds of extremist Trump-backers smashed into the Capitol building yelling threats against politicians and shutting down the legislature.
The suspect has also been identified, as 25-year-old Noah Green.
Capitol Police say that someone "rammed a vehicle into two USCP officers" and that a suspect was taken into custody.
Police block a street after a vehicle drove into police officers near the US Capitol building in Washington US
Evans is the seventh Capitol Police member to die in the line of duty in the department's history, according to the Officer Down Memorial Page, which tracks deaths of law enforcement.
Nearly 140 Capitol Police officers were wounded then, including officers not issued helmets who sustained head injuries and one officer with cracked ribs, according to the officers' union. "On behalf of the entire House, we are profoundly grateful", Pelosi added. One of the officers who was injured was taken by police auto to the hospital; the other was being transported by emergency medical crews, the officials said.
The U.S. Capitol complex was placed on lockdown after the shooting and staff were told they could not enter or exit buildings.
The Capitol was locked down and a National Guard team was deployed as police instructed staff to remain indoors.
President Joe Biden left Washington earlier in the day for Camp David, the presidential retreat in Maryland.
Video from reporters at the scene posted on Twitter appeared to show a auto that had crashed into a barrier.
The crash happened at a security checkpoint that is typically used by senators and staff on weekdays, but lawmakers are away for recess.