Police have identified the suspect as Larry Dawson and believe that the weapon he brandished may have been a pellet gun as opposed to an actual firearm, according to a law-enforcement official.

Mr. Dawson, who has identified himself as a preacher from the Nashville, Tenn., area, was charged with assault with a deadly weapon and assault on a police officer while armed.

Mr. Dawson was in stable but critical condition Monday night and was to appear in the District of Columbia Superior Court upon his release from the hospital, police said.

A bystander suffered minor injuries and no police officers were injured, Capitol Police Chief Matthew Verderosa said.

Mr. Verderosa said Mr. Dawson was already known to law enforcement for frequenting the Capitol grounds and that investigators believe the incident was an isolated criminal act.

Last year, Mr. Dawson was charged with unlawful conduct on the Capitol grounds and with assaulting a police officer after he disrupted proceedings in the House of Representatives. The lawyer who represented him in that incident didn’t respond to phone calls or emails.

Mr. Verderosa said officials haven’t determined how many officers may have fired weapons at the man. A weapon was recovered from the scene. It wasn’t immediately known if the incident was captured on security video.

The police chief added that the incident showed that the current screening process worked well.

Parts of the Capitol Complex were reopened midafternoon after being temporarily on lockdown, while the visitors center, where the incident took place, remained closed.

The visitors center is an underground complex adjacent to the Capitol where tourists go through security to visit the Capitol complex.

Congress was in recess this week, but the Capitol remains a popular attraction during the spring, when tourists come to Washington for the cherry-blossom season and spring-break trips.

Security was also increased at other several government buildings in Washington, with occupants temporarily ordered to stay in place.

Security was briefly tightened at the White House during the annual Easter egg roll—a popular annual event that brings thousands of visitors to the White House grounds for games, stories and an Easter egg hunt.

White House press secretary Josh Earnest, who was in the midst of his daily briefing when the situation unfolded, declined to comment.

Across the street from the Capitol, the U.S. Supreme Court briefly locked its doors, allowing neither tourists nor staffers in or out. The court reopened to visitors shortly after 3 p.m., a spokeswoman said.

A lockdown order at the U.S. Capitol is relatively rare. In one instance, in October 2013, a woman was shot dead after she rammed her car into security posts near the White House and was pursued by police, prompting a confrontation that ended in gunfire near the U.S. Capitol complex.

In a 1998 incident, a man with a history of mental problems killed two U.S. Capitol Police officers after he stormed through a security checkpoint and then opened fire. The incident underscored the need for enhanced security, leading to the construction of the visitors center, which opened in 2008.

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