The Army staff sergeant who allegedly went on a rampage and killed 16 Afghans as they slept in their homes had a traumatic brain injury at one point and had problems at home after his last deployment, officials told ABC News.

But the soldier, who is based at Fort Lewis in Washington, was considered fit for combat duty and deployed to Afghanistan in December, officials said.

Details about the staff sergeant, who has not been identified, emerged as the Taliban vowed revenge against “sick-minded American savages” after the mass killing.

What has trickled out about the suspect is that he was 38 and serving on his fourth combat deployment in 10 years, the first three in Iraq. He was on his first tour in Afghanistan, where he’d been since December.

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