WASHINGTON (AP) — A Capitol Police officer was killed Friday after a man rammed a car into two officers at a barricade outside the US Capitol and then emerged wielding a knife. It was the second line-of-duty death this year for a department still struggling to heal from the January 6 insurrection.

Video shows the driver of the crashed car emerging with a knife in his hand and starting to run at the pair of officers, Capitol Police Acting Chief Yogananda Pittman told reporters. Authorities shot the suspect, who died at a hospital.

“I just ask that the public continue to keep US Capitol Police and their families in your prayers,” Pittman said. “This has been an extremely difficult time for US Capitol Police after the events of January 6 and now the events that have occurred here today.”

Police identified the slain officer as William “Billy” Evans, an 18-year veteran who was a member of the department’s first responders unit.

President Joe Biden said in a statement that he and his wife were heartbroken to learn of the attack and expressed condolences to Evans’ family. He directed flags at the White House to be lowered to half-staff.

Two law enforcement officials told The Associated Press that investigators initially believed the suspect stabbed one of the officers, but it was later unclear whether the knife actually made contact, in part because vehicle struck the officers with such force. The officials were not authorised to publicly discuss the investigation and spoke on condition of anonymity.

Authorities said there wasn’t an ongoing threat, though the Capitol was put on lockdown for a time as a precaution. There was also no immediate connection apparent between Friday’s crash and the January 6 riot.

Law enforcement officials identified the suspect as 25-year-old Noah Green. Investigators were digging into his background and examining whether he had any mental health history as they tried to discern a motive. They were working to obtain warrants to access his online accounts.

Pittman said the suspect did not appear to have been on the police’s radar. But the attack underscored that the building and campus — and the officers charged with protecting them — remain potential targets for violence.

The crash and shooting happened at a security checkpoint near the Capitol typically used by senators and staff on weekdays, though most were away from the building for the current recess. The attack occurred about 100 yards (91 metres) from the entrance of the building on the Senate side of the Capitol. One witness, the Rev Patrick Mahoney, said he was finishing a Good Friday service nearby when he heard three shots ring out.

The Washington region remains on edge nearly three months after a mob of insurrectionists loyal to former President Donald Trump stormed the Capitol as Congress was voting to certify Biden’s presidential win.

Five people died in the January 6 riot, including Capitol Police officer Brian Sicknick, who was among a badly outnumbered force trying to fight off the intruders seeking to overturn the election. Authorities installed a tall perimeter fence around the Capitol and for months restricted traffic along the roads closest to the building, but they had begun pulling back some of the emergency measures. Fencing that prevented vehicular traffic near that area was only recently removed.