Ohio — Law enforcement agents shot and killed a man they claimed attempted to enter into the FBI’s Cincinnati headquarters on Thursday after an hour-long standoff that shut down a motorway and disrupted rural life.

Authorities in Ohio declined to confirm the man’s identity or explain his intentions. But, two law enforcement sources with knowledge of the situation indicated that inquiries were being made into the possibility that Ricky Shiffer, who they have named, had connections to extremist organizations, including one responsible for the attack on the Capitol on January 6.

Someone using an account with Mr. Shiffer’s name wrote posts on Mr. Trump’s social media site, Truth Social, the day after the FBI investigated the former president’s Florida residence.The attack in Ohio happened three days after Mar-a-Lago, Mr. Trump’s club and seaside residence, had a search warrant served on it, and one day after the FBI director told reporters that threats made online against federal law enforcement organizations are “regrettable and dangerous.”

At 9 a.m., the man—who authorities claimed was wearing armor—attempted to break through the visitor screening area outside the FBI’s Cincinnati Field Office in the neighborhood of Kenwood, according to Todd Lindgren, a bureau spokesman. Agents responded after an alarm, he claimed.

The FBI field office in Cincinnati on Thursday after a gunman attempted to enter the building.Credit: Jeffrey Dean/Reuters

After fleeing, the man drove north on Interstate 71, officials said, where he was spotted by a state trooper at a rest stop about 20 minutes later. That soldier began a chase and came under gunfire, Lt. Nathan Dennis of the Ohio State Highway Patrol.

The chase eventually exited the Interstate and meandered along rural roads before coming to a stop near an Interstate 71 overpass near the city of Wilmington. Lieutenant Dennis said gunfire was exchanged. He said officers attempted to negotiate with the man and then attempted to subdue him with less than lethal ammunition. These efforts failed. The man eventually raised a gun, Lieutenant Dennis said, and officers opened fire, mortally wounding him.

The attack came during a week when many Republicans had criticized the FBI for searching Mr. Trump’s home, with some calling it a dangerous Justice Department weapon. Some figures on the right also called for more widespread violence and civil war.

On Thursday night, Christopher A. Wray, the FBI Director, defended the FBI and condemned attacks on law enforcement.