FORT HOOD, Texas (AP) -- Investigators say they may never determine what caused Spc. Ivan Lopez to go on a deadly shooting rampage at Fort Hood, despite evidence that suggests an argument ignited the incident.
That rampage left three other soldiers dead and 16 wounded before the gunman took his own life.
Chris Grey, a spokesman for the Army's Criminal Investigation Command based in Quantico, Va., said the military has not established a "concrete motive" for Spc. Ivan Lopez's rampage.
And because Lopez is dead, Grey says it may never know.
Lt. Gen. Mark Milley, Fort Hood's commander, said an "escalating argument" precipitated the assault, even though investigators believe Lopez made no effort to target specific soldiers.