Officer William Evans, an 18-year veteran of the force, was killed after Noah Green, 25, ploughed his auto into a security barrier on Capitol Hill on Friday afternoon before leaping out with a knife.
Two law enforcement sources involved in the investigation told BBC partner CBS News that Noah Green was from Indiana.
Green is a follower of Nation of Islam, said MSNBC, quoting Facebook content that was believed to be published by him. The authorities have not yet affirmed the suspect's identity or specified a motive.
The attacker, a 25-year-old IN resident called Noah Green, rammed his vehicle into two officers, injuring one and killing the other.
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The deceased officer has been identified as William "Billy" Evans who had joined the force in March 2003 and was a member of the First Responder's Unit.
As Congress is not now in session, most politicians were not at the Capitol complex at the time of the attack.
President Joe Biden had just departed the White House for Camp David when the incident occurred.
The FBI said in a statement its Washington Field Office is responding and providing support to Capitol Police. The Driver of the crashed auto emerged with a knife in his hand and started to run towards the officers.
"At such time the suspect exited the vehicle with a knife in hand".
The exact cause of the police officer's death was not immediately clear.
The incident occurred about 100 yards (91 meters) from the entrance of the building on the Senate side of the Capitol.
There was a heavy police response outside of the Capitol, including a helicopter landing on the premises.
It was the second line-of-duty death in Capitol Police this year. Capitol Police officer, Brian D. Sicknick, died a day after rioters supporting former President Donald Trump stormed Capitol on January 6 "due to injuries sustained while on-duty". Fencing that prevented vehicular traffic near that area was recently removed as the Capitol has started to open up after the January 6 riots.