U.S. Defense Secretary Chuck Hagel joined military leaders Tuesday to place a wreath at the Navy Memorial honoring the 12 victims of the Navy Yard shooting.
Hagel and Joint Chiefs of Staff Chairman Gen. Martin Dempsey placed the wreath next to the "Lone Sailor" statue at the memorial on Pennsylvania Avenue during a brief, sober ceremony as a bugler played "Taps," the American Forces Press Service said.
The mourners included by Navy Secretary Ray Mabus and Washington Mayor Vincent Gray.
Early Tuesday, authorities cleared the final people at the Washington Navy Yard to go home after a former Navy reservist's murderous rampage.
About 2,000 people were held on the base Monday night, waiting for permission to leave, Navy officials said.
The FBI interviewed every person leaving the former shipyard and ordnance plant in southeast Washington, said Vice Adm. Bill French, the head of all Navy installations.
Officials late Monday released the names of seven of the 12 people killed: Michael Arnold, 59; Sylvia Fraiser, 53; Kathy Gaarde, 62; John Roger Johnson, 73; Frank Kohler, 50; Kenneth Bernard Proctor, 46; and Vishnu Pandit, 61. The names of the other victims will be released when family notifications are completed.
SWAT teams still found people hiding on the base late Monday, The Washington Post reported. Some of the people had remained hunkered down in hideouts since the 8 a.m. attack, the newspaper said.
Despite concerns about a second suspect in the mass shooting, authorities said Monday night they believed the shooting was the act of lone gunman Aaron Alexis, 34, a New York native who lived in Fort Worth, Texas, and was working for a military subcontractor.
Alexis was killed in a gun battle with police that ended the mayhem.
Three weapons were found with the gunman -- a Colt AR-15 5.56mm, magazine-fed semi-automatic assault rifle; a shotgun and a semiautomatic pistol, authorities said.
The shooting, which wounded at least five people, was the second-deadliest mass murder on a U.S. military base, after the November 2009 mass shooting at Fort Hood in Texas that left 13 people dead.
The Navy Yard shooting was also the deadliest mass murder in the Washington, D.C., area since the Sept. 11, 2001, attack on the Pentagon, which killed 184 people.
The dead from Monday's shooting ranged in age from 46 to 73 years old, officials said.
Authorities said they were still seeking a motive for the killings. They asked the public for help by posting pictures of Alexis on the FBI website.
The agency said it was treating the shooting as a criminal investigation, not one linked to terrorism.
French warned March 21 that one of the side-effects of the federal government's budget sequestration would be a reduction in Navy Yard security, Army Times reported at the time.
The shootings occurred in Building 197 of the sprawling base.
Building 197, where about 3,000 people work, serves as the headquarters for Naval Sea Systems Command , one of the Navy's five commands and the one responsible for overseeing the construction of many of the Pentagon's largest vessels.
Alexis received a general discharge from the Navy Reserve in Fort Worth two years ago, a designation that usually signals a problem in his record.
"There is no question there was a pattern of misconduct," a defense official told several news organizations.
The official said Alexis was pushed out of the military after a 2010 arrest for firing a gun at his Fort Worth apartment. The incident sent a bullet into a neighbor's property a few days after an alleged confrontation with the neighbor over noise.
No one was injured and no charges were filed, said the Tarrant County Criminal District Attorney's Office in Fort Worth.
Alexis had told police "he was trying to clean his gun while cooking and that his hands were slippery," said the police report, cited by The Wall Street Journal.
Alexis was also arrested but not charged in a 2005 Seattle gun incident, officials said.
Despite his record, he had a security clearance with a military contractor that gave him access to the Navy Yard, the officials said.
The Navy Yard was reopened Tuesday for only essential personnel, CBS News said.