WASHINGTON -- Someone fired shots at the Pentagon early Tuesday in what security officials described as "a random event."
No one was injured in the pre-dawn incident in which shots were fired into two windows at the sprawling Defense Department just across the Potomac River in suburban Virginia.
Steven Calvery, director of the civilian Pentagon Force Protection Agency, told reporters that a number of his officers reported hearing five to seven shots fired about 3:55 a.m. near the south parking lot of the Pentagon. The Pentagon building and the roads leading it were briefly shut down as officers did an initial sweep of the area.
An internal search of the iconic structure found fragments of two bullets still embedded in two windows -- one on the third floor and one on the fourth.
The bullets had shattered but did not penetrate the windows, Calvery said. The windows were part of offices that are being renovated and they were unoccupied at the time.
Calvery said he didn't know what kind of weapon was used but that it was probably a high-velocity rifle. No suspects were arrested, he said.
"Right now we consider this a random event," he said.
But he also 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. The museum is associated with the Quantico Marine Base, some 30 miles south of the Pentagon.
A rifle is also believed to have been used in that shooting, which may have occurred during early morning hours.
Pentagon investigators worked with the FBI as well as Arlington, Va. police, who helped sweep of the area, and Virginia State Police, who closed part of nearby Interstate 395 to search for evidence.
A dozen officers at around 9 a.m. walked side-by-side in a line as they combed through a grassy area on the south side of the building.
Calvery said investigators were talking to some construction workers who also heard the shots. He said it was possible the shooter had stood on the roof of a nearby building.
A spokesman for Prince William County Police, which is investigating the museum incident in Quantico, said his officers were working with the Pentagon force protection agency and were trying to determine if the two shootings were related.
A cleaning crew at the museum called police Monday when they noticed the bullet holes in a part of the building that faces Interstate 95.
Gwenn Adams, a spokeswoman for the museum, said it appeared to have been hit by at least 10 rounds -- five that struck glass and five marks on metal panels. Not all the bullets penetrated the glass, she said.
The marks are high on the imposing 118,000 square-foot structure, Adams said. The museum did not receive any kind of threatening communication or messages before discovering the bullet scars, she said.
Police believe the shots were fired at the museum late Saturday or early Sunday, when no one was inside.
Investigators used a crane to inspect the damage Monday. Because of the height of the holes, police said they suspected the bullets were fired from a rifle. They were still working to determine the caliber of the bullets.
None of the museum's artifacts -- including a harrier jet hanging near the damaged windows -- was hit.
In early March a gunman opened fire at a Pentagon security checkpoint, wounding two police officers. John Patrick Bedell, 36, of Hollister, Calif., was shot by police and died hours later.
State, federal and local agencies were cooperating in studying surveillance video and questioning witnesses in connection with Tuesday's shooting.
Associated Press writer Matthew Barakat in McLean, Va., contributed to this report.