US National Guard members stand guard in front of the U.S. Capitol building in Washington, D.C., the United States, on April 2, 2021. (Xinhua/Liu Jie)

One of the two police officers hit by a car ramming into barriers surrounding the U.S. Capitol complex on Friday afternoon was pronounced dead, Acting Chief of Capitol Police Yogananda Pittman said.

Pittman said at a news conference that the driver exited the vehicle with a knife, started lunging at the Capitol police and was shot by the police. The suspect was pronounced dead after being transported to the hospital.

The exact cause of the police officer's death is not immediately clear.

Robert Contee, acting chief of the Metropolitan Police Department, said the incident "does not appear to be terrorism related."

"It does not appear to be terrorism related. But obviously we'll continue to investigate to see if there is some type of nexus along those lines," Contee said at the news conference.

The U.S. Capitol went into lockdown due to the "exterior security threat" following the incident, which took place around 1:30 p.m. eastern time.