Army Secretary John McHugh testified Thursday that the soldier appeared to have no connections to extremist groups.
The soldier is identified by others as Ivan Lopez. He enlisted in the Army in June 2008 as an infantryman and later switched his specialty to truck driver, the job he had in Iraq.
McHugh says the soldier was examined by a psychiatrist last month and was found to show no violent or suicidal tendencies. He says the soldier had been prescribed Ambien to deal with a sleeping problem.