A jury of US army officers has convicted Major Nidal Hasan on all 13 charges of premeditated murder and all 32 charges of attempted premeditated murder for the November 2009 shooting spree at Fort Hood, Texas.
Friday's convictions mean Hasan could face the death penalty by lethal injection.
The jury will begin hearing the penalty phase of the court-martial on Monday and make a recommendation to the judge, who will determine the sentence.
The military isn't big on executing people ... Since the end of World War II, very few people have been executed.
The US military has not executed a service member since 1961.
"The military isn't big on executing people," says Lieutenant Colonel Gary Solis, a retired Marine court judge. "Since the end of World War II, very few people have been executed."
According to the US military, there are five servicemen awaiting death sentences at Fort Leavenworth.
Three of them have appeals pending in military courts.
"Those cases are reviewed and reviewed, and the sentence keeps getting knocked down from death to life without parole," Solis said. "I don't expect to see them executed anytime soon."
Hasan, an American-born Muslim and acting as his own defence lawyer, admitted in his opening statement to killing 13 people and wounding 31, saying he switched sides in what he considered "a US war on Islam".
Al Jazeera's Heidi Zhou Castro, reporting from Fort Hood, said many survivors of the attacks and relatives of the victims found it unfair that Hasan was not tried on charges of "terrorism".
"They say that the US government is putting political correctness above justice, that because Hasan is an American-born Muslim, the military did not want to single him out," she said.
Prosecutors opted against bringing "terrorism" charges against Hasan, who at one point during the trial told the judge his attack was motivated by "an illegal war" and that he had "adequate provocation" to launch the attack on soldiers readying to deploy to Iraq and Afghanistan.
Al Jazeera's Jamie Tarabay contributed to this report.