JUDY WOODRUFF: Our lead story is yet another mass shooting in the United States, this time at a Navy complex in the heart of Washington, D.C.
A hail of bullets shattered a September morning at the heavily guarded site. When it ended, a dozen victims were dead, and at least one gunman had been killed.
PATRICIA WARD, eyewitness: It was like pow, pow, pow. And in a few seconds, it stopped, and then it pow, pow, pow, pow. So we just ran.
JUDY WOODRUFF: Patricia Ward was in the cafeteria of Building 197 when the shooting began. Others told of a gunman on the third floor of the building.
MAN: There's a group of us. And he aimed a gun and fired our way.
WOMAN: He was far enough down the hall that we couldn't see his face, but we could see him with the rifle, and he raised and aimed at us and fired, and he hit high on the wall just as we were trying to leave.
QUESTION: What was going through your mind?
WOMAN: Get everyone out of the building right now.
JUDY WOODRUFF: The killing and chaos erupted shortly after 8:00 this morning at the headquarters of the Naval Sea Systems Command, less than two miles from the U.S. Capitol Building. Dozens of police and emergency response vehicles swarmed the facility within minutes.
Flights were temporary grounded at Reagan National Airport so they wouldn't interfere with helicopters circling the Navy Yard complex. As the day wore on, District of Columbia Police confirmed one shooter had died at the Navy Yard site. He was identified at Aaron Alexis, a 34-year-old Texan.
The FBI's Valerie Parlave appealed for help in flushing out his background.
VALERIE PARLAVE, FBI: This remains a very active investigation. We currently have our evidence response team moving in to process the scenes where the shootings took place. We will also continue to run down every lead and we will continue to work together on this investigation with our law enforcement partners. Again, we ask the public to look at the photos of the deceased shooter and to contact the FBI with any and all information.
JUDY WOODRUFF: Investigators also searched for another man wearing a military-style uniform, but his role, if any, was unclear.
At the White House, less than four miles away, President Obama called the shooting a cowardly act and pledged a full investigation. D.C. officials said they had not yet determined the motive. Mayor Vincent Gray said there is no reason to think terrorism was involved.
Meanwhile, family members rushed to the shooting scene, desperately seeking news of loved ones.
WOMAN: A nervous wreck, but much better now that I know he is safe.
JUDY WOODRUFF: And the wounded were taken to local hospitals. The Washington Hospital Center received three victims. The shooting forced a number of schools to go on lockdown. And, hours later, everyone inside the U.S. Capitol itself to stay indoors for a time. In addition, the Washington Nationals canceled their baseball game tonight. Their stadium is not far from the Navy Yard.