Images from a traffic helicopter show a handcuffed person in a hooded sweatshirt sitting down with their head bowed.
Officials said there was no continuing threat after the morning incident, which left a black sport utility vehicle riddled with what appeared to bullet holes, according to video from the scene.
US President Donald Trump has been briefed on the incident.
He did confirm that one person had been injured and transported, although he did not say where the person had been transported to.
"Meade", and the White House offered thoughts and prayers with those who have been affected, spokeswoman Lindsay Walters said. "We will continue to provide updates as they become available".
EFF co-founder John Perry Barlow dead at 70
Barlow and Weir met as teenagers and formed a lifelong friendship that took on a new level once Weir joined the Grateful Dead . A Wyoming native, Barlow brought together both the counter-cultural and libertarian strains in early internet ideology.
Fort Meade, which includes the NSA campus, said a "police investigation" is ongoing and a highway in the area is closed.
In this image made from video and provided by WUSA TV-9, authorities investigate the scene of a shooting at Fort Meade, Md. on February 14, 2018.
Dave Fitz, an Federal Bureau of Investigation spokesman, said the agency was "aware of the incident" and its Baltimore unit was responding.
About 7:30 a.m., Anne Arundel County police said in a Twitter message that there was a "possible shooting" near NSA. The investigation into the attack is now underway.
In March 2015, one person was killed and another seriously wounded after driving a vehicle up to the NSA's gate, ignoring commands to stop.