Police are searching for answers into why a military veteran went on a deadly shooting rampage Monday at a U.S. naval facility in Washington. Twelve people were killed before the gunman was fatally shot by police.
There were moments of remembrance in the nation's capital Tuesday, honoring the 12 civilians killed and those wounded during Monday's rampage at Washington's Navy Yard. U.S. Defense Secretary Chuck Hagel laid a wreath at the Navy memorial.
On Capitol Hill, the flag flew at half staff as lawmakers paused for a moment of silence.
Senate Majority Leader Harry Reid said, "My thoughts are with those who are suffering as a result of the loss of their loved ones and also those people recovering from the wounds."
Just blocks from the Capitol, police pored over evidence at the crime scene.
On Monday, though, it was frantic as police rushed to the Navy Yard building after the first shots were fired.
Investigators say that's where Aaron Alexis, a former Navy reservist and civilian contractor used a valid ID to enter the command building armed with a shotgun. Witnesses say he was perched on a fourth floor balcony and shot at people below in a cafeteria. Police say officers engaged Alexis in a gun battle for more than 30 minutes before he was killed.
Police Chief Cathy Lanier described the officers as heroic.
"It's a horrible tragedy, and we hope it never happens again anywhere, much less in Washington, D.C. But I think the goal that we have is if it does happen, is to stop that harm as quickly as we possibly can and we met that goal," she said.
The FBI is looking at the gunman's past and events that may point to behavioral problems including two other shooting incidents in the last nine years. Authorities say family members have told them Alexis was seeking treatment for mental problems.
FBI Assistant Director Valerie Parlave said, "We continue to conduct interviews, exploit digital media and run down every lead we can to piece together his recent movements and determine the motive behind his attack."
In the New York City neighborhood where Alexis' family lives, there was shock and sympathy from those who know the gunman's mother.
A neighborhood resident said, "I know she is devastated that he killed 12 people and he got killed. So you know it's a tragic incident for the family and the community, you know, as a whole."
Back at the Naval Yard, some who witnessed the shooting say they are ready to return to work.
"Our hearts go out to the folks, and we will go back to work when the base is open again. We will do what we do each day to the best of our ability," said one Navy Yard worker.
In wake of the shooting, the Defense Department has ordered a review of security and access procedures at military facilities worldwide.