Transcript for Did Afghan Deaths Change Course of War?
There are around 90000 Americans in Afghanistan tonight and many of them have spent many years trying to prove to the locals that they are the good guys. That effort took a massive step backwards this weekend when a lone soldier put on -- night vision goggles walked to a nearby village and allegedly murdered sixteen civilians. Including nine children. As presidents and generals wrestle with the ramifications there's new scrutiny on the troubling legacy of the suspect's home base. Here's ABC's Martha -- When he wasn't -- war that 38 year old staff sergeant accused of massacring innocent Afghans was based here. Joint base Lewis McCord outside Tacoma Washington. A base that is seen as one of the most troubled in the military. A history of violence during deployment and after. Sargent Calvin Gibbs convicted of murdering Afghans for -- leading and organizing soldiers into what was called a kill -- 24 year old Iraq veteran Benjamin Barnes made it back to Lewis McCord. But after a shoot out at a New Year's party this year he fled to nearby Mount Rainier. And gunned down -- park Granger. Last year Sargent -- -- poured lighter fluid on his wife. And set her on fire and the list goes zone and -- one of the -- but now the community is faced with the worst crime of all. Trying to understand. Column married father of two could. As officials say he did slaughter Afghan women and children. I can't get anybody in the -- who say they going to killing 1618. Civilians and children -- Is -- anywhere in the world. Much less when you're here we're in an -- by -- -- Unacceptable. But all too real the images from half -- world -- chillingly clear. Sixteen Afghan citizens dead nine of them young children some just -- -- Their bodies wrapped in blankets by the killer and pepper and -- neither are my children Taliban this grieving woman asks. Is my two year old Taliban. The massacre allegedly began in the middle of the night Saturday 3 AM. When officials say the soldier -- night vision goggles lefties remote combat outpost south west of Kandahar. He allegedly walked one mile through the darkness to the village of -- land deep and there they say went house to house. Four were killed in the first none were arm. In the second house this soldier allegedly killed 114 girls for boys and three women many of them in their sleep. A look at an element adding that they are all my neighbors in villagers this man says you wiped out any -- your family. But the shooter wasn't done officials say he then -- Back past his base to another village. Killing one more unarmed victim in his final brutal act what happened what causes soldiers snap. That'll need to be determined -- in the days and weeks to come. The staff sergeant enlisted in the army just two months after terrorists brought down the world trade towers on 9/11. A trained sniper he spent the better part of the past decade at war. Four deployments three deployments to Iraq from 2003 to 42006. To seven. And the last in a rock from 2009. To 2010. It was in 2010. That the soldier suffered. A traumatic brain injury when his vehicle rolled over in Iraq he was later treated and cleared again for combat. But when he returned home officials say had a hard time just -- home life it would marital problems that officials say have persisted. -- he continued to clear routine behavioral health screenings. He was sent to Afghanistan. In December 2011. This is unprecedented in American history where -- professional military has been at war for so long no matter the motive. This could not have come at a worse time only weeks after the country exploded in the wake of the the accidental burning of -- by American soldiers. Today President Obama. Urged patience as we transition there can lead we don't rush for the exits in a way that could end up leading to more deaths -- more disaster. But it has now been over a decade of war and -- Are evident everywhere. More than 76000. Cases of post dramatic stress disorder. Have been identified in the army alone investigators will look at the staff sergeants background and what care he got in the field. And back at joint base Lewis -- The army medical facility -- -- Madigan is already being accused. Of reversing more than 200 PT SD diagnosis. In order to save money. But the army today released a statement saying to take a small number of unconnected incidents over time. And present them as evidence of a troubled military community. Does a disservice. The murder charges against the staff sergeant are expected. Any -- then we'll know his name for now he has retained a lawyer and he's saying nothing about what happened. For Nightline I'm Martha Raddatz in Washington.
This transcript has been automatically generated and may not be 100% accurate.