Capitol police said they were responding to reports that someone rammed a vehicle into two officers and a suspect was in custody.
The suspect died at a hospital, officials said.
Just months after the January 6 riot, Capitol Hill has once again come under emergency lockdown as breaking reports of the shooting of two Capitol Police officers surfaced on social media.
"The DC National Guard deployed a Immediate Response Force (IRF) composed of National Guard soldiers and airmen to the Capitol complex this afternoon to support the U.S. Capitol Police", according to a tweet from the National Guard Bureau Public Affairs Press Desk.
Update: Law enforcement sources have told ABC News that the suspect is dead.
Members of Congress were not in Washington on Friday, with both the Senate and House of Representatives in recess for the Easter holiday.
"This has been an extremely hard time for US Capitol Police after the events of January 6 and now the events that have occurred here today", said Mr Pittman.
"My thoughts and prayers go out to the family, friends, and colleagues of the U.S. Capitol Police Officer who lost his life today protecting the very symbol of our democracy", Mayorkas said in a statement Friday. "Both officers are injured".
US Capitol Police have just identified the officer killed by a driver who rammed into a Capitol barricade on Friday.
U.S. Capitol Police officers stand near a vehicle that crashed into a barrier on Capitol Hill in Washington, D.C., Friday.
US Capitol Police say all Capitol buildings were being locked down "due to an external security threat" and staff members were told they could not enter or exit the buildings.
In this video screengrab, two stretchers can be seen being brought out to tend to two officers in the U.S. Capitol complex.
The incident came amid tightened security in Washington after the January 6 insurrection by supporters of then-president Donald Trump.
Authorities said that there was no longer an ongoing threat and that the attack did not appear to be related to terrorism.
The security checkpoint is typically used by senators and staff on weekdays, but lawmakers are away for recess.
Video posted online showed a dark colored sedan crashed against a vehicle barrier and a police K-9 inspecting the vehicle. Fencing that prevented vehicular traffic near that area was recently removed, but there was additional interior fencing between the checkpoint and the building.
President Biden was in Camp David, Md., when the incident took place, according to the White House.
Man rams vehicle into police officers near US Capitol
This time, one officer was killed and a second hospitalized after a driver rammed a security checkpoint on the Capitol grounds. One person has died after slamming a vehicle into the security barrier surrounding the Capitol building, U.S. media report .
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Taiwan train crash kills 41 in deadliest rail tragedy in decades
The island's worst crash in recent history was in 1991, when 30 passengers were killed and 112 injured after two trains collided. Reportedly, the Taroko Express is one of the fastest train services in Taiwan and typically travels at around 80 miles per hour.
Taiwan train crash leaves 36 dead, several injured
Those were said to be the worst previous crashes on the railway system that dates from the late 19th century. Taiwan's President Tsai Ing-wen said a number of people are trapped, according to the BBC .