The jury of 13 high-ranking officers took about seven hours to reach the verdict. In the next phase, they also must all agree to give Hasan the death penalty before he can be sent to the military's death row, which has just five other prisoners. If they do not agree, the 42-year-old will spend the rest of his life in prison.
Hasan, a Virginia-born Muslim, said the attack was a jihad against U.S. wars in Iraq and Afghanistan. He bristled when the judge suggested the shooting rampage could have been avoided were it not for a spontaneous flash of anger.
"It wasn't done under the heat of sudden passion," Hasan said before jurors began deliberating. "There was adequate provocation -- that these were deploying soldiers that were going to engage in an illegal war."
All but one of the dead were soldiers, including a pregnant private who curled on the floor and pleaded for her baby's life.
The attack ended when Hasan was shot in the back by one of the police officers responding to the shooting. He is now paralyzed from the waist down and uses a wheelchair.
Hasan planned to continue representing himself in the sentencing phase, which was expected to include more testimony from survivors of the attack inside an Army medical center where soldiers were waiting in long lines to receive immunizations and medical clearance for deployment.
Hasan began the trial by telling jurors he was the gunman, but he said little else, which convinced his court-appointed standby lawyers that Hasan's only goal was to get a death sentence.
The military called nearly 90 witnesses, but Hasan rested his case without calling a single person to testify in his defense and made no closing argument. He did, however, leak documents to journalists that revealed him telling military mental-health workers that he could "still be a martyr" if executed.
Death sentences are rare in the military and trigger automatic appeals that take decades to play out. Among the final barriers to execution is authorization from the president. No American soldier has been executed since 1961.
Hasan spent weeks planning the Nov. 5, 2009, attack. His preparation included buying the handgun and videotaping a sales clerk showing him how to change the magazine.
He later plunked down $10 at a gun range outside Austin and asked for pointers on how to reload with speed and precision. An instructor said he told Hasan to practice while watching TV or sitting on his couch with the lights off.
When the time came, Hasan stuffed paper towels in the pockets of his cargo pants to muffle the rattling of extra ammo and avoid arousing suspicion. Soldiers testified that Hasan's rapid reloading made it all but impossible to stop the shooting. Investigators recovered 146 shell casings inside the medical building and dozens more outside, where Hasan shot at the backs of soldiers fleeing toward the parking lot.
In court, Hasan never played the role of an angry extremist. He didn't get agitated or raise his voice. He addressed Osborn as "ma'am" and occasionally whispered "thank you" when prosecutors, in accordance with the rules of evidence, handed Hasan red pill bottles that rattled with bullet fragments removed from those who were shot.