President Obama and his generals told a crowd of 3,000 soldiers Tuesday that the Fort Hood massacre stands as an incomprehensible military tragedy one that happened "in the comfort of home."

"These Americans did not die on a foreign field of battle. They were killed here, on American soil, in the heart of this great state, in the heart of this great American community," Obama said during an outdoor memorial service for the 12 soldiers and one civilian killed in Thursday's shooting rampage.

"It is this fact that makes the tragedy even more painful and even more incomprehensible," he said.

The president, flanked by other dignitaries, spoke on a stage in the sprawling front lawn of the 3rd Corps Headquarters building. It was at this post that an Army major was alleged to have opened fire inside a soldiers' processing center.

At the foot of the stage, 13 pairs of boots of the slain soldiers were laid next to 13 combat helmets perched on M-16 assault rifles. Portraits of those killed sat next to each rifle.

"Here, at Fort Hood, we pay tribute to 13 men and women who were not able to escape the horror of war, even in the comfort of home," Obama said.

The suspect, Army Maj. Nidal Malik Hasan, continued to recover from multiple gunshot wounds at the Brooke Army Medical Center in San Antonio.

Lt. Gen. Robert Cone, the post's commander, told the crowd that victims ranged in age from 19 to 62 and came from 11 different states. Between them, they left 19 children behind. One was pregnant.