President Barack Obama will be part of the memorial service late Sunday afternoon to honor the men and women killed in the Washington Navy Yard shooting.
The service is being held at the Marine Barracks Washington in southeast Washington, not far from the Navy facility where authorities say 34-year-old Aaron Alexis fatally shot a dozen people last Monday morning. Police killed Alexis in a gun battle.
The president and first lady Michelle Obama will also visit with the victims' families.
The dead range in age from 46 to 73, and include civilian employees and contractors. Eight people were also hurt, including a police officer and two others who suffered gunshot wounds.
Obama spokesman Jay Carney says the president wants to mourn the loss of life and share in the nation's pain after another mass shooting.
The service is closed to the public, says barracks spokesman Capt. Jack Norton. About 4,000 people have been invited, he said.
As authorities searched Monday for the gunman, Obama lamented that "we are confronting yet another mass shooting, and today, it happened on a military installation in our nation's capital." He said the gunfire targeted military and civilian personnel, men and women who were going to work and doing their jobs.
Addressing an awards dinner Saturday night in Washington, Obama said these families "now know the same unspeakable grief of families in Newtown, and Aurora, and Tucson, and Chicago, and New Orleans, and all across the country, people whose loved ones were torn from them without headlines sometimes, or public outcry."
But he said that kind of violence is happening every day. He urged supporters "to get back up and go back at it" to push gun control legislation that stalled in the Senate earlier this year, part of a package of measures Obama promised to push after the December killing of 20 first-graders and six educators at an elementary school in Newtown, Conn.
"As long as there are those who fight to make it as easy as possible for dangerous people to get their hands on a gun, then we've got to work as hard as possible for the sake of our children," Obama said, in a likely preview of his remarks Sunday. "We've got to be ones who are willing to do more work to make it harder."
The Navy Yard itself re-opened for normal operations on Thursday, three days after the shooting. The building where the shooting took place remains closed.
Obama has taken on the role of the nation's chief consoler several times already this year, and many more times throughout his nearly five years in office.
This year, he led the mourning for victims of an explosion at a fertilizer plant in West, Texas, and a double bombing at the finish line of the Boston Marathon. He also consoled victims of a major tornado that flattened the town of Moore, Okla.
Obama also has mourned victims of other mass shootings, including in Newtown, Conn., and at shopping mall in Tucson, Ariz., that severely wounded then-Rep. Gabrielle Giffords.
Based on reporting by the Associated Press.