Photos emerged on social media appearing to show a black van at the building’s entrance and a handcuffed man, possibly an attacker, sitting on the ground. Bullet holes are seen in the windshield of the van, which seems to have crashed into a barrier.

The FBI has sent personnel to respond to the incident, FBI Baltimore said on Twitter. The NSA says the incident is under control, according to local media citing the agency’s spokesman.

Highway MD 32 is closed in both directions, local authorities said on Twitter. Drivers have been advised to take alternate routes and “expect long delays.”