One of two injured U.S. Capitol Police officers has died after being hit by a suspect who then rammed their car into the north barricade of the Capitol complex Friday afternoon before exiting the vehicle with a knife, acting Chief Yogananda Pittman said at a press conference.
Police opened fire and the suspect is dead, Pittman said.
"The suspect exited the vehicle with a knife in hand. Our officers then engaged that suspect. He did not respond to verbal commands," Pittman said. After the suspect lunged at officers, they "fired upon the suspect."
The officer who died of injuries sustained at the scene has been identified as 18-year Capitol Police veteran William "Billy" Evans.
"He began his USCP service on March 7, 2003, and was a member of the Capitol Division’s First Responder’s Unit. Please keep Officer Evans and his family in your thoughts and prayers," Pittman said.
The suspect who was killed by Capitol Police has been identified as Noah Green, law enforcement sources told ABC News.
Authorities believe Green, 25, had ties to Virginia and Indiana, law enforcement sources said.
Authorities are taking a close look at social media postings believed to be associated with Green. No clear motive has been established, sources said.
Multiple agencies are investigating the incident, including the Capitol Police, D.C. Metropolitan Police Department and the FBI Washington Field Office. The FBI Indianapolis Field Office is also providing support and assisting law enforcement partners in the investigation.
The other officer last was reported in "stable and non-threatening condition."
The Capitol was put on lockdown Friday afternoon. Hill staffers were sent a message from U.S. Capitol Police around 1:20 p.m. saying that "due to an external security threat ... no entry or exit is permitted." The message said people could move around inside the building "but stay away from exterior windows and doors. If you are outside, seek cover."
"We do not have the suspect on file with U.S. Capitol Police," Acting Metro Police Department Chief Robert Contee said. "So there is no indication at this time that there is any nexus to any member of Congress."
Conte also said the incident didn't appear to be terror related.
Congress was in recess when the incident occurred, and many staff offices were closed in observance of Good Friday.
There were approximately 2,300 National Guardsmen already on mission at the Capitol following the violent riot on Jan. 6, when protesters breached the Capitol -- five people died, including Capitol Police officer Brian Sicknick.
The D.C. National Guard deployed an "Immediate Reaction Force" to support Capitol Police during Friday's incident, according to a spokesperson.
About 40 National Guardsmen lined up with riot gear to block access to Constitution Avenue, just east of where the incident took place. Capitol Police and the National Guard also blocked off roads and pedestrian access near the Supreme Court.
House Speaker Nancy Pelosi ordered flags at the Capitol lowered to half-staff in honor of the officer who died, a spokesperson for Pelosi said in a tweet Friday.
President Joe Biden also issued a proclamation ordering flags to be flown at half-staff through Tuesday at the White House and on federal grounds in Washington, D.C.
In a statement, the president said he and the first lady were “heartbroken” over the deadly attack.
“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 statement said.
Pittman also asked that the public "keep U.S. Capitol police and their families in your prayers."
"This has been an extremely difficult time for U.S. Capitol police after the events of January 6 and now the events that have occurred here today. So I ask that you keep our U.S. Capitol police family in your thoughts and prayers," she said.
ABC News' Mariam Khan, Alexandra Svokos, Luke Barr, Benjamin Siegel, Justin Gomez and Josh Margolin contributed to this report.