Security officials say a shooting at the Pentagon Tuesday morning was "a random event."

No one was injured as someone fired shots at the building around 4:55 a.m. ET.

Officials found fragments of two bullets still embedded in two windows. The bullets shattered, but did not penetrate the windows, according to Steven Calvery, director of the civilian Pentagon Force Protection Agency.

No suspects have been arrested.

Police don't believe the incident was part of a larger plot. However, Calvery said authorities were looking at whether the shooting was related to Monday's discovery of bullet holes in windows at the National Museum of the Marine Corps. in Triangle, Va. -- about 30 miles south of the Pentagon.