In the first village, more than a mile south of the base, he allegedly killed four people in the first house. In the second house, he allegedly killed 11 family members -- four girls, four boys and three adults.
According to a member of the Afghan investigation team and ABC News' interviews, he then walked back to another village past his base and killed one more person. He reportedly returned to the base on his own and turned himself in calmly.
An official told ABC News that the soldier had suffered a mild traumatic brain injury (TBI) in the past, either from hitting his head on the hatch of a vehicle or in a car accident. He reportedly went through the advanced TBI treatment at Fort Lewis and was deemed to be fine.
He also underwent mental health screening necessary to become a sniper and passed in 2008. He had routine behavioral health screening after that and was cleared, the official said.
When the soldier returned from his last deployment in Iraq he had difficulty reintegrating, including marital problems, the source told ABC News. But officials concluded that he had worked through those issues before deploying to Afghanistan.
On Thursday, Browne said that Bales' marriage was "fabulous."
Afghan political leaders have called for the shooter to be tried publicly in Afghan courts, but U.S. military officials say the case will be handled in U.S. military courts. A U.S. military official says Afghan officials were made aware of the transfer before it occurred.
The Associated Press contributed to this story.