(CNN) The FBI is investigating the military background and social media history of a 22-year-old man who is suspected of trying to shoot up a federal building in Dallas Monday.

Brian Isaack Clyde was shot and killed by federal officers before he got a chance to enter the Earle Cabell Federal Building, authorities said.

No officers or other citizens were injured in the shooting on the south side of the building, police said. One worker sustained a superficial injury when she was taking cover, US Attorney Erin Nealy Cox said. She added that there were 300 federal workers inside the building during the shooting.

Clyde was taken to a hospital where he was declared dead, according to FBI special agent in charge Matthew J. DeSarno.

DeSarno said at a press conference that Clyde was discharged from the Army in 2017. The US Army confirmed to CNN that Pfc. Brian Clyde served as an infantryman from August 2015 to February 2017.

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