The soldier detained for the shootings in Afghanistan was a qualified infantry sniper, a senior Department of Defense official told CNN. (See also: heightened security in Afghanistan)

The soldier was injured in a vehicle rollover while in Iraq in 2010, according to the official. The official described it as a non-combat rollover. He was diagnosed with Traumatic Brain Injury (TBI) but was found fit for duty.

His family has been moved on to Joint Base Lewis-McChord for their safety, the official said.

After an Afghan soldier alerted the U.S. military at the base of the soldier's initial departure, the U.S. military put up an aircraft to search for the missing soldier. Soon after, Afghan civilians came to the gate carrying wounded civilians, the first indication the military had of the shooting.

When the soldier turned himself over to the search party, he immediately invoked his rights not to speak. He has been moved to Kandahar and put in pre-trial confinement, a congressional source told CNN.