Army Staff Sgt. Robert Bales arrived at the military prison at Fort Leavenworth, Kan., on Friday to await trial for the nighttime massacre of 16 unarmed Afghan villagers, including nine children, that unfolded earlier this month. As military prosecutors decide on the exact charges Bales will face, and while the soldier's civilian and military lawyers work out a defense case, reporters have been busy filling in some of the blanks about the life of the 38-year-old married father of two. Here's what we know about Bales so far:

What was Bales like before he joined the Army?
He grew up in the Cincinnati suburb of Norwood, Ohio, the youngest of five children. Bales graduated from high school in 1991, then attended the nearby College of Mount St. Joseph for a year and Ohio State University for three, but didn't graduate. In May 1999, Bales, his brother Mark, and a third man started a financial firm in Florida, which they dissolved 16 months later. Less than two months after the Sept. 11, 2001, terrorist attacks, Bales enlisted in the Army. Bales "said joining the military was something he had to do," says childhood friend Michael Blevins. "He couldn't just keep making money." 

What do we know about his time at war?
Bales served in Iraq three times for a total of 37 months between 2003 and 2010, and deployed for Afghanistan in December 2011, beginning his fourth tour of duty. His commanding officers and fellow soldiers in Iraq describe him as a steady, unflappable, exemplary soldier. "He’s one of the best guys I ever worked with," Army Capt. Chris Alexander tells the AP. "He is not some psychopath. He's an outstanding soldier." According to an Army statement, Bales had been cited several times for superior performance on tough missions, earning six Army Commendation Medals, three Good Conduct Medals, and two Meritorious Unit commendations. 

How about his personal life?
While stationed at Joint Base Lewis-McChord outside Tacoma, Wash., Bales met and married his wife, Kari. They have two young children, both born while Bales was serving in Iraq. The couple owned two homes, a duplex they apparently abandoned a few years ago, and a four-bedroom house in a wooded community outside Tacoma. Kari Bales put the latter property on the market three days before her husband's alleged March 11 rampage, for about $50,000 less than the purchase price they'd paid in 2005. Kari notes in personal blogs she kept that Robert was denied promotion in 2011, and that the family didn't want him to return to combat for a fourth tour.

Why did Bales allegedly snap?
Some theorize it was the financial strain and emotional toll of being away from his family. Bales also has a history of legal black marks — a 2002 arrest for assaulting a girlfriend, dismissed after he underwent 20 hours of anger management training; a 2005 drunk-driving arrest; and a 2008 hit-and-run incident in which he rolled his car and fled to the nearby woods, bloody and in uniform, before paying $1,000 to have the case dismissed. But the most common theory? Bales is suffering from post-traumatic stress disorder (PTSD), possibly from a concussive head injury he sustained in Iraq.

What is Bales' likely defense?
His civilian attorneys, John Henry Browne and Emma Scanlan, have raised the possibility of using PTSD as a defense. But while that may help mitigate the sentences, "it's an uphill battle in the military and civilian court," retired Col. Bruce White tells Stars and Stripes. A RAND Corp. study from 2008 estimated that almost 20 percent of soldiers returning from Iraq and Afghanistan have PTSD or major depression. And the stresses Bales faced are not unique to him, military defense lawyer Michael Waddington tells The Washington Post.

Where will his trial be held?
Bales' military trial will be held somewhere in the U.S., and Afghan witnesses may be flown in to testify.

Sources: AP (2), Bloomberg, Christian Science Monitor, New York Daily News, New York Times, Washington Post