Unlike the first Fort Hood mass shooting, yesterday’s tragic incident has no apparent connection with terrorism, but instead seems to be a case of mental illness. Spec. Ivan Lopez had been under evaluation for “behavioral health and mental health issues,” perhaps related to his four-month tour of duty in Iraq three years ago:

Unfortunately, the intervention did not come in time to prevent his attack on fellow soldiers, which stopped when an MP confronted him:

An Iraq war veteran who was grappling with mental health issues opened fire at Fort Hood, Tex., in an attack that left four people dead and 16 wounded Wednesday afternoon, according to preliminary law enforcement and military reports. The gunfire sent tremors of fear across a sprawling Army post still reeling from one of the worst mass shootings in U.S. history.

Many basic details about the shooting remained unclear in the chaotic hours after the first calls for help around 4 p.m., but senior U.S. law enforcement officials said the incident did not appear to be linked to any foreign terrorist organizations. The shooter was among those who died, the officials said. …

Milley said the shooter “had behavioral health and mental health issues.” He said the soldier, who self-reported a traumatic brain injury and was taking anti-depressants, had been under examination to determine whether he had post-traumatic stress disorder. “We are digging deep into his background,” Milley said.

Milley said the soldier opened fire with a .45-caliber Smith & Wesson semiautomatic pistol that was purchased recently but was not authorized to be brought on the post. He was eventually confronted by a female military police officer. He put his hands up but then pulled out a gun from under his jacket. “She engaged,” Milley said, and then the soldier put the gun to his head and shot himself.

Why didn’t the Army identify Spec. Lopez as a threat? The Pentagon is already asking itself that question, the Washington Post reports:

It unfolded just two weeks after the Defense Department unveiled the findings of three investigations into last year’s fatal shooting at a Navy Yard building by a contractor and four years after a similarly extensive probe into a massacre at Fort Hood by an Army psychiatrist led to vows of sweeping reforms.

Although there was little information late Wednesday about the possible motives of the gunman or the circumstances that preceded the shooting, former and current service members were shocked to learn that the Army post where Maj. Nidal Malik Hasan fatally shot 13 fellow service members in Nov. 2009 had once again become the scene of carnage.

“We do not yet know how or why this tragedy occurred, but nearly five years after the Nidal Hasan shooting at Fort Hood in 2009, it is clear that we must do far more to ensure that our troops are safe when they are at home on base,” Rep. Tom Rooney (R-Fla.), a former Army lawyer who was based at Fort Hood, said in a statement. “We must thoroughly investigate what happened today, so that we can take whatever action is necessary to prevent something like this from ever occurring again.”

Four years ago, the DoD pledged to “develop a scientifically based list of behavioral indicators of potential violence,” based on what it had learned from the Nidal Hasan attack. However, as last year’s Naval Yard shooting and yesterday’s incident demonstrates, they have yet to develop a predictive model. Perhaps that’s because all three were perpetrated by very different kinds of attackers, with what seems to be different pathologies. While these predictive models may hold some value, it seems unlikely that it would achieve significant protection without becoming a kind of “pre-crime” unit, accusing people who will never act out violently at all and ruining lives in a different way.

If Lopez suffered from PTSD from his service in Iraq, though, the answer might be the fact that it took this long to identify it, let alone treat it. At least according to the Post’s report, he left Iraq in 2011, meaning that the Army had more than two years to detect and treat the issue. That might be one place to start in looking to prevent these kinds of incidents in the future, although it has to be stressed that even though they are tragic and shocking, they are also exceedingly rare — which is another reason they are difficult to prevent.

The local CBS affiliate updated viewers on the sixteen wounded in the shooting, three of whom are in critical condition:

For those who want to assist but live outside the area, a donation to the local Red Cross might be one option.

Update: The Army refutes the claim that Lopez was being treated for PTSD, or that he was a combat veteran at all. He was being evaluated for PTSD unrelated to combat, but was being treated for depression, and prescribed Ambien while the Army evaluated his claim that he suffered a traumatic brain injury while in Iraq:

Army secretary: Fort Hood suspect treated for depression, anxiety and sleep disturbances; was prescribed Ambien. http://t.co/JDz2pTAo2v

— CNN Breaking News (@cnnbrk) April 3, 2014

But behind Lopez’s smile lay a history of depression, anxiety and other psychiatric disorders, according to Milley, and he was receiving treatment and taking antidepressants.

He had served for four months in Iraq in 2011. And while Army records don’t show him as having been wounded there, Lopez himself reported that he had suffered a traumatic brain injury, Milley said.

And he was undergoing diagnosis procedures for post-traumatic stress disorder.

“He was not diagnosed, as of today, with PTSD,” Milley said.