Vice President Kamala Harris condoled the death of US Capitol Police Officer William Evans, saying that he "made the ultimate sacrifice protecting the Capitol and those who work there on behalf of the American people."
Evans died while another police officer was hospitalised after a car crashed into a security barrier at the US Capitol complex after which the driver lunged towards the officers with a knife, police said. The officers opened fire and the suspect was shot dead.
"Officer Evans, his family, and all those who knew him are in our hearts and prayers. We mourn with them during this difficult time," the US vice president said in the statement.
"Doug and I are grateful for the Capitol Police, the National Guard Immediate Response Force, and everyone else who responded swiftly to today's attack," Harris, who served in the Senate for four years, said.
"And we continue to be proud of the courageous men and women who defend the Capitol, especially during a challenging period when they have faced two violent and deadly attacks," she said.
Harris also said, "In an inexplicable act of violence, a brave US Capitol Police Officer, William Evans, was killed in the line of duty while another officer fights for his life. Officer Evans made the ultimate sacrifice to protect the Capitol. Our hearts go out to his family and loved ones."
Earlier on Friday, the White House flag was lowered to half-staff following the death of the the 18-year US Capitol Police veteran.
US President Joe Biden reacted to the incident saying he and first lady Jill Biden were heartbroken.
"Jill and I were heartbroken to learn of the violent attack at a security checkpoint on the US Capitol grounds, which killed Officer William Evans of the US Capitol Police, and left a fellow officer fighting for his life," Biden said.
"We send our heartfelt condolences to Officer Evans' family, and everyone grieving his loss. We know what a difficult time this has been for the Capitol, everyone who works there, and those who protect it," the President said.
The US Capitol went into lockdown on Friday (local time) after the incident at the North Barricade vehicle access point along Constitution Avenue outside the iconic building.
Federal and Law enforcement sources told CNN that the suspect in the attack was 25-year-old Noah Green from Indiana.
"It is with profound sadness that I share the news of the passing of Officer William 'Billy' Evans this afternoon from injuries he sustained following an attack at the North Barricade by a lone assailant," Acting Police Chief Yogananda Pittman of the US Capitol Police (USCP) said.
"Just after 1 pm, a man in a blue sedan rammed his vehicle into the North Barricade at the US Capitol, striking 2 USCP officers. The Department immediately locked down the Capitol Campus," according to a statement by the US Capital Police.
"The man exited the vehicle with a knife and ran toward our officers. At least one officer drew their weapon and shot the suspect. One USCP officer was transported by a USCP cruiser to the hospital. The second USCP officer was transported by DC Fire and EMS. The suspect was also transported by DC Fire and EMS to the hospital where he succumbed to his injuries around 1:30 pm," the police said.
The incident follows recent ramping down of some additional protective measures that were put into place after the January 6 insurrection at the Capitol Hill complex.