April 2 (UPI) -- Authorities put the U.S. Capitol complex on lockdown Friday after a car rammed into a barricade, leaving a police officer and a suspect dead, authorities said.
The attacker drove into a barricade north of the Capitol, at the intersection of Constitution Avenue and Delaware Avenue, around 1 p.m., Yogananda Pittman, acting chief of Capitol Police, said in a news conference. Officers shot the driver after he got out of his vehicle with a knife and ran "aggressively toward officers," she added.
"It is with a very, very heavy heart that I announce that one of our officers has succumbed to his injuries," Pittman told reporters.
She identified the slain officer as William "Billy" Evans, an 18-year veteran of the force, and member of the Capitol Division's First Responder's Unit.
"Please keep officer Evans and his family in your thoughts and prayers," Pittman said in a statement.
A second Capitol Police officer was injured and was transported to an area hospital. Their name wasn't released.
CNN reported at least one of the officers was stabbed in the attack, though it's unclear which one.
Capitol Police locked down all buildings in the complex and shut down streets in the area. The lockdown was lifted around 3:30 p.m.
Acting Metropolitan Police Chief Robert Contee said there wasn't an ongoing threat and the attack didn't appear to be terrorism-related.
"But obviously we'll continue to investigate to see if there is some type of nexus along those lines," he told reporters.
The FBI's Washington field office was providing support to Capitol Police in their investigation.
President Joe Biden said he received briefings on the incident from his homeland security adviser. He ordered the U.S. flag to be down at half-staff in honor of the slain officer.
First lady Jill Biden "and I were heartbroken to learn of the violent attack at a security checkpoint on the U.S. Capitol grounds, which killed Officer William Evans of the U.S. Capitol Police, and left a fellow officer fighting for his life," Joe Biden said.
"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."
Drew Hammill, House Speaker Nancy Pelosi's deputy chief of staff, issued a statement earlier in which she ordered Capitol flags to be flown at half-staff.
"Speaker Pelosi has ordered the flags at the U.S. Capitol to be flown at half-staff due to the death of a U.S. Capitol Police Officer in the of duty today," he tweeted. "The process of lowering the flags may take longer than usual because of the Capitol's current lockdown status."
The Bidens traveled earlier in the day to Camp David, where they planned to spend Easter weekend.
The incident comes nearly three months after thousands of former President Donald Trump's supporters attacked the U.S. Capitol in an attempt to overturn the results of the 2020 presidential election.
Capitol Police officer Brian Sicknick died in the insurrection, and two others who responded to the incident -- Capitol Police officer Howard Liebengood and Metropolitan Police officer Jeffrey Smith -- died by suicide in the days after. Four participants in the riots also died.
"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," Pittman said. "So I ask that you keep our U.S. Capitol police family in your thoughts and prayers."