The wife of Staff Sgt. Robert Bales defended her husband in an interview with Matt Lauer for NBC's Today, set to air Monday.
The Washington state woman said her husband joined the Army after the terror attacks of Sept. 11, 2001, to "protect his family, friends and country. He wanted to do his part." that her husband is "very brave, very courageous."
Officials say Bales wandered off base in southern Afghanistan earlier this month and killed eight Afghan adults and nine children.
The wife of the Joint Base Lewis-McChord soldier said the accusations are "unbelievable to me."
"He loves children, he's like a big kid himself," she said. " I have no idea what happened, but he would not ... he loves children, and he would not do that."
He was formally charged Friday with 17 counts of premeditated murder and other crimes.
U.S. investigators have said they believe Bales killed in two episodes, returning to his base after the first attack and later slipping away to kill again. He is reported to have surrendered without a struggle.
The 38-year-old married father of two from Lake Tapps, Wash., is being held at a U.S. military prison at Fort Leavenworth, Kan.
Karilyn Bales has spoken to her husband by telephone twice since he was detained. The soldier called his wife first from overseas shortly after massacre, and then last week from Fort Leavenworth where the two talked about family matters and "reaffirmed their love for each other," said her attorney, Lance Rosen.
The couple has two young children, a girl named Quincy and a boy named Bobby.
Bales was on his fourth tour of duty in a war zone, having served three tours in Iraq, where he suffered a head injury and a foot injury. His civilian attorney, John Henry Browne, had said the soldier and his family had thought he was done fighting.
The family has set up a defense fund to help pay for Bales' legal fees.
The Bales family had a Seattle-area home condemned, struggled to make payments on another and failed to get a promotion a year ago. Karilyn Bales put the family's Lake Tapps, Wash., home up for sale days before the rampage.
The youngest of five brothers, Bales grew up in the working class Cincinnati suburb of Norwood, Ohio, and has been described as cheerful, all around good guy. He joined the Army two months after 9/11, after a Florida investment business failed and after he had worked with a string of securities operations.