• Just after 13:00 local time, a suspect rammed a car into the North Barricade entrance to the Capitol
• The suspect then emerged with a knife and was shot after lunging towards police
• No known nexus to terrorism has been identified and the suspect was not previously known to police
• The suspect and one Capitol Hill police officer have both died. Another officer was injured
• The suspect has not yet been identified
• The attack comes less than three months after a violent mob stormed the Capitol on 6 January, seeking to overturn the presidential election result
• Barricades erected since that attack have begun to come down, but over 2,000 National Guard troops deployed since January remain on Capitol Hill

Samantha Granville
BBC News, Capitol Hill

Capitol Hill has been tense over the past three months.

Since the riot on 6 January the Capitol Hill complex has been like a fortress.

Barbed wire, metal fencing and tonnes of security.

Less than three months from that day, we are back here with blocked roads, extra troops and a solemn feeling.

Congress is in recess today and staffers I’ve spoken to are grateful to be home and are nervous about returning to work after the Easter holiday.

It’s scary to have your workplace attacked twice, they say.

It’s concerning for them that even with security ramped up, an event like this still happened that led to an officer's death.

Media are camping out about a block away from the main Capitol building.

As no one is allowed in or out of the perimeter, we expect the Capitol to stay on lockdown for the next couple of hours.

Lawmakers may not be on Capitol Hill right now but they are busily tweeting their reaction to today's news.

Speaker of the House Nancy Pelosi has ordered flags at the Capitol to fly at half-staff, after news an officer was killed.

"Today's incident at the Capitol reminds us of the threats still facing our nation," tweeted Michigan Republican Fred Upton.

"My thoughts are with these brave officers and their families," wrote Democrat Eric Swalwell. "They’ve sacrificed a tremendous amount over the last few months and we are forever indebted to them."

Scores of other lawmakers also tweeted their thoughts and prayers for the injured officers.

National Guard troops have been at the US Capitol since the attack on 6 January.

Some have gone back, but a spokesperson for the Washington DC National Guard has confirmed about 2,300 troops remain in DC.

The spokesperson confirmed the Guard have deployed a "Quick Reactionary Force" around the complex.

Video shows Guard members lining up to protect the complex in the immediate aftermath of the shooting.

Image source, Getty Images

Police chief Pittman said the incident did not appear to be terrorism-related.

The investigation remains in its preliminary stages, she said, but "it does not appear that he is known" to Capitol police.

She added that there did "not appear to be an ongoing threat".

Nevertheless, the security posture of police would remain in a "steady state", she said.

With "a heavy heart", Pittman announced one officer had succumbed to his injuries.

Acting chief of the US Capitol Police Yogananda Pittman says the suspect rammed his car into two officers and slammed into the North Barricade of the complex.

The suspect then exited with a "knife in hand" and lunged at the officers, at which time an officer opened fire.

The suspect was taken into custody and died in hospital.

She added that it had been "an extremely difficult time" for members of the US Capitol Police since the attack on 6 January.

She asked people to "keep US Capitol police and their families in your prayers".

Image source, Getty Images

Image source, Getty Images

The US Capitol is largely empty, as lawmakers from both the House and the Senate are on their Easter recess.

Most have gone home for the holiday, but a few lawmakers remain in town.

A short while ago, Democratic congressman Ro Khanna spoke to CNN from his vehicle. He said he had received "a frantic call" from his staff about the shooting while going out to grab Chinese takeout.

"Going to work is a dangerous thing in the United States of America now," he said, adding that it brought back bad memories of the attack on 6 January.

In addition to Khanna, several congressional reporters are also inside the building complex.

The Capitol police are now addressing the press.

Friday’s incident has recalled another attack at the Capitol that happened all too recently – the 6 January riot.

Following a speech by then-President Donald Trump, supporters marched to the Capitol in protest at the 2020 election.

At the time, lawmakers were inside the building, certifying Joe Biden’s win.

The situation turned violent when the protesters broke into the building, attacking police and searching for lawmakers.

Rioters made it all the way to the Senate floor as members of Congress and then-Vice President Mike Pence had to be rushed to safety.

That day saw five people killed, more than 100 officers injured and millions of dollars in damage to the building at the heart of America’s democracy.

The riot also led to Trump’s second impeachment. In the months since, hundreds of people have been arrested in connection with the attack.

These were the scenes from that attack

Just after 13:00 local time, an alert went off that had not been sounded since the 6 January attack.

Staff members, including Aaron Fritschner who works for Democrat Don Beyers, began receiving email and voice alerts telling them to stay away from doors and windows and to remain inside Capitol buildings.

Congress is not currently in session, but staff working on the Hill were going about their business day.

National Guard troops and police officers have put in place a large barrier at the crime scene.

Here's as close as the BBC's Samantha Granville could go.

The US Capitol police say they will be briefing the press outside the Capitol at 14:45 EST (18:45 GMT).

The suspect in the attack has died in hospital, sources told the BBC's US broadcast partner CBS News.

The person has not yet been named.

US Capitol Police say two of their officers were injured after being rammed by a blue sedan car.

According to reports, the driver then emerged and began threatening people with a knife before being shot.

Three people, including the suspect, were transported to hospital.

The incident comes weeks after Congress began removing razor wire fencing and barricades erected after the 6 January attack on Congress while they were certifying Biden's election victory.

Welcome to our live coverage of today's incident at the US Capitol, where buildings are on lockdown after a vehicle slammed into security barriers.

Lawmakers are in recess right now, making it unlikely that any were close to the scene of the attack.

However, staff members and journalists are still on Capitol Hill today.

President Biden left Washington earlier today for the Camp David presidential retreat in Maryland.