Washington (CNN) -- A Pentagon official said he believes the shooting early Tuesday at the U.S. Defense Department headquarters was a "random incident".
"We are looking at all the possibilities," Steven E. Calvery, director of the Pentagon Force Protection Agency, said at a press conference late Tuesday morning. "What we have is an isolated incident, so far".
Pentagon police officers, as well as several construction workers in the area, heard at least five shots fired around 4:50 a.m., Pentagon officials said.
As of midday Tuesday, authorities had discovered two bullet fragments in third- and fourth-floor windows on the south side of the building, said Calvery. That part of the Pentagon was empty at the time of the shooting, as it is in the process of being renovated. The bullets shattered but did not go through the windows, which are bulletproof, according to Calvery.
The early-morning shooting prompted a 40-minute shutdown of the entire Pentagon, and authorities conducted an interior sweep of the building shortly after 6 a.m.
Calvery said authorities were unsure who fired the shots and with what kind of gun, though he said he believes they came from a rifle.
CNN
