Shots were fired early Wednesday at the ultra-secret National Security Agency, the US electronic spying agency outside Washington, leaving one person injured, officials said.
Aerial footage of the scene from NBC News showed a black SUV with numerous bullet holes in its windshield crashed into concrete barriers at the main entrance to the NSA's headquarters in Fort Meade, Maryland.
The images showed what appeared to be police surrounding a man on the ground in handcuffs.
"The situation is under control and there is no ongoing security or safety threat," the NSA said.
"We can confirm there has been one person injured and we don't know how the injuries occurred," an NSA spokesman told AFP.
The local ABC television affiliate put the number of injured at three and said a suspect was arrested.
The Baltimore office of the Federal Bureau of Investigation, which is handling the investigation, said the incident "has been contained."
A law enforcement source told AFP that it was too soon to know whether the incident was an attack on the facility or otherwise.
They are "still trying to ascertain the facts," the source said.
"The president has been briefed on the shooting at Ft Meade," the White House said in a statement. "Our thoughts and prayers are with everyone that has been affected."