Identified as Spc. Ivan Lopez by Lt. Gen. Mark Milley, Ft. Hood's commanding general, the Army veteran reportedly walked into one of the area buildings with a .45 semi-automatic handgun and started shooting. He kept firing even as he used a vehicle to make his way to another building, where the gunfire continued.
When military police confronted him, Lopez put his hands into the air before pulling out his gun from his jacket and shooting himself in the head.
According to the AP, an investigation into the gunman’s mental health background was initiated immediately after the violence ended. Part of the probe will also focus on the possibility that a fight or argument triggered the shooting.
"We have to find all those witnesses, the witnesses to every one of those shootings, and find out what his actions were, and what was said to the victims," a federal law enforcement official said to the AP on condition of anonymity.
In a press conference Wednesday evening, Lt. Gen. Mark Milley confirmed that the shooter was being treated for numerous health issues after being transferred to Fort Hood in February. Lopez was also being evaluated for post-traumatic stress disorder in connection to his four months spent in Iraq in 2011, though he had yet to be officially diagnosed.
There was strong evidence that the shooter had a medical history that indicated an unstable psychological condition, said Milley. There was a "strong possibility" that a verbal altercation with another soldier had preceded the shootings, he added, although there was no indication specific people had been targeted in the shooting. Lopez had been prescribed anti-depressants and the sleep aid medication Ambien.
Obviously, we are digging deep into his background," Milley said to ABC News. "He was undergoing behavioral health, psychiatric treatment for depression and anxiety and a variety of other psychological and psychiatric issues. ... He was not diagnosed, as of today, with PTSD, he was undergoing a diagnosis process to determine if he had PTSD. That is a lengthy process."