The U.S. soldier accused of killing 16 Afghan civilians over the weekend is not talking and is generally not cooperating with investigators, U.S. military officials said Tuesday as details of his arrest began to emerge in a case that could lead to an insanity plea or possibly the death penalty.
On Sunday, the soldier, whose name is being withheld until charges are filed, reportedly walked off the U.S. base in Kandahar province -- where he had been stationed for just six weeks -- and allegedly entered homes in a nearby village, shooting people while they slept. Nine children and three women are among the dead, and some of whose bodies were apparently burned.
Shortly afterward, local Afghans showed up at the outpost looking for help. The military began searching for a suspect.
According to a U.S. military source, aerial imagery was used to spot the accused soldier crawling on the ground near his base. The imagery was likely provided a drone, though the official did not say. The soldier was seen lying on the ground and then getting up, according to the imagery. He was then apprehended.
One U.S. official told Fox News there is "reason to believe alcohol may have been involved."
The soldier has invoked his rights to an attorney, but it's not clear yet whether he has retained one, either private or military.
As the details unfold, President Obama on Tuesday pledged that the U.S. will "spare no effort" in conducting the investigation
"The United States takes this as seriously as if it was our own citizens, and our children, who were murdered. We're heartbroken over the loss of innocent life," Obama said during a White House event.
"I've directed the Pentagon to make sure that we spare no effort in conducting a full investigation," Obama said. "We will follow the facts wherever they lead us and we will make sure that anybody who is involved is held fully accountable with the full force of the law.
As the news trickled out across Afghanistan, the alleged massacre has already generated threats of violence. On Tuesday, an Afghan delegation sent by President Hamid Karzai to investigate the shooting scenes were attacked by militants. Multiple people were wounded and one Afghan soldier was killed, a senior military official in Afghanistan told Fox News.
The Taliban, with whom the U.S. and Afghan officials are said to be negotiating, has vowed revenge, including reportedly threatening to behead American soldiers.
Though Afghanistan's parliament has called for the soldier to be tried in an Afghan court, he will likely be returned to the United States and face a general court-martial under the Uniform Code of Military Justice. Pentagon investigators are mulling charges that could result in the death penalty if he is found guilty.
The soldier reportedly suffered a traumatic brain injury, incurred during one of his three prior tours in Iraq. Military officials later described it as a mild injury resulting from a vehicle rollover but his history could impact the case, said Gary Solis, a Georgetown University law professor and expert on war crimes and the military justice system
Solis said he thinks there's "a good chance" that an insanity defense will be raised.
"Given the circumstances of this case and the previous records of deployments of this staff sergeant, I think it's an obvious defense of his defense counsel," Solis told Fox News.
"It's hard to say whether the case will even go to trial because in war crimes like this it's very possible that there will be ... an insanity defense, that he is unable to recognize the wrongfulness of his act because of a severe mental disease or injury," Solis said.
Solis, a former Marine military prosecutor, said that the military is well aware of the side effects of multiple deployments in war zones, including post-traumatic stress disorder, the high divorce rate and the spousal abuse rate, among others. He said PTSD and insanity are not the same, and PTSD is not a defense, but "the groundwork has been laid" by his repeated deployments to declare insanity.
"Those individuals with PTSD should not ever be confused with someone who is insane, but insanity is much more than that, and one merely looks at the acts that this individual allegedly committed to say this is just not the working of a rational mind," Solis said.
President Ronald Reagan reinstituted the death penalty for soldiers by executive order in January 1984. In the order, he required that the president personally sign-off on an execution before it can take place. Though the last time a soldier was put to death -- for rape and murder -- was in 1961, six military members are currently on death row.
Solis said death sentences are relatively rare in the Armed Services. More common is for charges to be brought under a sentence of life without the possibility of parole.
If the accused soldier doesn't claim an insanity defense, he may be able to use insanity as a mitigating factor to avoid death. He could also argue that his long service to the nation makes him eligible for a milder sentence.