In addition to the 13 killed, 30 were hospitalized and at least eight more wounded but released by emergency rooms.

Lt. Gen. Robert Cone, commander of III Corps and Fort Hood, briefed reporters Monday about the service that begins at 1 p.m. today. He said President Barack Obama and his wife, Michelle, will arrive on Air Force One during the morning, attend the service and fly out midafternoon.

During the night Sunday crews built a secluded area on Sadowski Field next to III Corps headquarters by placing hundreds of 10-by-12 metal overseas shipping crates in a huge box formation to create a secure and private space that will hold about 3,000 mourners.

"We are creating an environment back there that is kind of private and free of observation," Cone said.

Mourners will include the families who lost loved ones, their extended families, the wounded who are able to attend, and soldiers and their comrades, Cone said.

"I don't know what the impact has been to the larger Fort Hood population, so part of helping the grieving process is to invite as many folks as we can," Cone said. "That is why we created this venue."

Gates will open at 10 a.m. for those wanting to attend the memorial service.