Videos from inside the congress building show how police and security guards are forced back by the rioters and attacked with pipes and spray bottles.
One of the police officers on the scene, 42-year-old Brian Sicknick, was so seriously injured that he later died in hospital.
Exactly what caused his death is unclear, but according to two police sources, Sicknick was hit in the head by a fire extinguisher, writes the news agency AP.
Brian Sicknick has been part of the Capitolium's police force since 2008 and before that worked for the US National Guard in New Jersey.
- Our sympathies and thoughts go to his family.
Those responsible for this should be held accountable.
They will do that, says Joe Biden in a televised speech.
Security officers resign
The security officials for the Capitolium have been criticized for calling in only for a peaceful demonstration, despite warnings of a possible riot and plenty of resources.
On Thursday, Chief of Police Steven Sund, along with two other senior security officials, resigned following pressure from House Speaker Nancy Pelosi and other congressional leaders.
In addition to Brian Sicknick, 35-year-old Ashli Babbitt was shot dead by police during the storm and three more people died from what police describe as "medical conditions."