Washington — A Secret Service agent shot and critically wounded a man outside the White House on Friday afternoon after he approached a guard booth carrying a small, silver pistol and refused to put it down, according to law enforcement officials.

Lines of tourists were frantically ushered away from the area as heavily armed police converged on the publicly accessible security shack near 17th and E streets NW. The White House was put on lockdown, and Vice President Joe Biden was secured inside the complex, authorities said. President Obama was golfing at Joint Base Andrews at the time.

Authorities said the man, who was shot once in the chest, was hospitalized in critical condition Friday night. Two law enforcement officials identified him as Jesse Olivieri, a Pennsylvania man in his 30s. His relatives could not immediately be reached for comment.

Police released no other details about him or an apparent motive. Authorities discovered ammunition for a .22-caliber weapon inside the man’s white sedan, which was parked near the scene, according to two law enforcement officials.

Friday’s apparent attempt to breach the White House grounds is another in a series of security incidents in recent years at or near the presidential complex. It took place against a backdrop of heightened global tension brought on by terrorist attacks and the ongoing wars in the Middle East and Afghanistan, and as officials were investigating the crash of an Egyptian passenger jet over the Mediterranean Sea.

Law enforcement officials said there was no immediate sign that the Friday incident, which occurred just after 3 p.m., had any links to terrorism.

The Secret Service said in a statement that the man approached the security gate holding a gun and that “officers gave numerous verbal commands for the subject to stop and drop the firearm. When the subject failed to comply with the verbal commands, he was shot once by a Secret Service agent and taken into custody.”

Officials said they recovered the man’s firearm.

Baltimore resident Akil Patterson, who was in a security line for the Eisenhower Executive Office Building, said he saw an officer come through a side door and overheard radio chatter: “Shots, shots fired, suspect down, suspect down.”

Jaspreet Singh said a friend, Ranjit Singh, texted him that: “A cop shot a guy.” In his text, the friend said he saw a man with a gun in his right hand walking toward a police officer before he was shot.

Federal agents with the Washington field office of the Bureau of Alcohol, Tobacco, Firearms and Explosives were helping to trace the weapon. Officials said that the man’s white, four-door sedan was found parked near 17th Street and Constitution Avenue NW, and an officer spotted the ammunition through a window.

Law enforcement officials noted that the man did not gain access to the White House complex. After the incident, police blocked streets between 16th and 17th streets NW, along with parts of the Mall near the Washington Monument. A helicopter circled overhead as tourists, office workers and people with White House appointments were quickly ushered away.

The Secret Service last year added small spikes — or “pencil points” — to the top of the six-foot fence that surrounds the White House complex after a series of climbing incidents.