A security guard at the Smithsonian Hirshhorn Museum and Sculpture Garden shot and killed himself Monday afternoon in a basement locker room, according to authorities.

The shooting forced hundreds of patrons to evacuate and drew a large contingent of federal and local police to the area. Smithsonian spokeswoman Linda St. John said the incident occurred about 3:05 p.m. in an area of the museum that is off limits to the public and well away from where any might wander.

She said the guard, who has not been identified, was 31 or 32 years old. He was alone at the time, she said, and shot himself with his department-issued service revolver.

The museum, located at 7th Street and Independence Avenue SW, normally closes at 5:30 p.m. It was still closed as of 4:15 p.m., and it was unclear whether it would reopen Monday.