Shots have been fired outside the headquarters of the National Security Agency, according to US media.
Three people were shot and a suspect was arrested in the incident outside America’s electronic espionage agency in Maryland, report local media.
Gunfire reportedly rang out after a black SUV pulled up at the entrance to the facility in Fort Meade.
An NSA spokesman was quoted as saying the situation was under control. Anne Arundel County police have responded.
CBS News images showed the vehicle with what appeared to be bullet holes in the front windscreen.
US President Donald Trump has been briefed on the incident, according to a White House spokeswoman.