The jury read out the Army staff sergeant’s fate at Joint Forces Base Lewis-McChord, near Seattle, where Bales had been stationed before deploying to Afghanistan, Reuters reported.
He pleaded guilty to the rampage during a June court appearance to avoid the death penalty. Authorities charged Bales with 16 counts of premeditated murder among 30 other charges.
The decision to be made on Friday was whether or not Bales would be eligible for parole after 20 years.
“He wiped out generations and he ruined lives forever,” prosecutor Lt. Col. Jay Morse said, according to Reuters. “He should be known by one official title from this day until the day he dies: inmate.”
The 40-year-old father of two from Ohio told the courtroom on Thursday he “hid behind a mask of bravado,” according to CNN.
“I’m truly, truly sorry to those people whose families got taken away,” Bales said, the Associated Press reported. “I can’t comprehend their loss. I think about it every time I look at my kids.”
Leading up to Bales' sentence, the jury heard from nine Afghan villagers who travelled 7,000 miles to tell the court about their lives since the attack.
Most were still angered by what happened last March and thought the life sentence given to Bales was not enough.
"We wanted this murderer to be executed," said Hajji Mohammad Wazir, who lost 11 family members in Bales's attack. "We were brought all the way from Afghanistan to see if justice would be served. Not our way — justice was served the American way."
Haji Mohammad Wazir lost six of his seven children, his wife and his mother.
“If someone loses one child, you can imagine how devastated their life would be,” he said, according to the AP.
Bales had served four tours in Iraq and Afghanistan prior to the attack. Defense attorneys said he suffered a brain injury and post-traumatic stress, and was drinking and taking illegal drugs to counteract family and professional frustrations.
The defense tried to portray him as a patriot who enlisted after 9/11, a devoted father and former high school quarterback.
Prosecutors pointed to his checkered criminal past that included a $1.5-million fraud judgement and two drunk-driving incidents, the AP said.
His attack was the worst by an American against civilians since the Vietnam War and endangered US troops and efforts in Afghanistan.