A shooting at Fort Hood in Texas, the second in five years, left four people dead, including the gunman, an Iraq war veteran identified as Ivan Lopez, who reportedly killed himself in front of police.

An investigation is underway by authorities at Fort Hood. According to The Washington Post:

They want to find out whether a fight or an argument preceded the shootings. They're also looking at the treatment the man received while he was being evaluated for post-traumatic stress disorder, though, no formal diagnosis had been made.

He was also being treated for depression and anxiety, authorities said.

Lt. Gen. Mark Milley, Fort Hood's commanding officer, said the man had self-reported a traumatic brain injury upon returning to the U.S. but he was not wounded in action.

Within hours of the attack, investigators started looking into whether the man's combat experience had caused lingering psychological trauma. Authorities will also speak to Lopez's wife, and plan to search his home and seize his computers. An official at a press conference last night explained that all the relevant federal agencies involved in the investigation are already looking for clues about Lopez's motivation on Facebook and Twitter.

The morning after the shooting, Sen. Jim Inhofe (R-Okla.) suggested restrictions on carrying firearms on base left victims defenseless during the shooting:

"I would just disagree with a lot of these gun control people who are trying to blame the gun and not the individual," Mr. Inhofe, Oklahoma Republican, told MSNBC's "Morning Joe."

He said when he was in the military, "we didn't have the restrictions that they have right now." The Washington Post explains the rules on carrying firearms at Fort Hood and other bases:

Soldiers on all military installations, including Fort Hood, are not armed while on post, nor are they permitted to carry any privately owned firearms. Only law enforcement and security personnel are allowed to have weapons on post.

On Fort Hood, the restrictions on personal weapons were expanded in the wake of the 2009 massacre and an epidemic of suicides on post, which is the largest active-duty armored post in the country. Current policy requires soldiers to register their own personal weapons with their commanders and to keep those weapons in the arms room. Nationwide restrictions on carrying firearms on base were first introduced in 1992.

In addition to expanding the restriction on carrying firearms after the 2009 shooting at Fort Hood, a report in the wake of that shooting also made other suggestions. Via USA Today:

[The report] recommended that the Defense Department update training and education and coordinate with the FBI, which has studied behavioral traits that might provide an early warning of potential violence.

The report also recommended that the Defense Department develop procedures to better share information among agencies so commanders would know of any adverse information in an individual's past. That report was released in 2010, and its recommendations began to be implemented a few months later. Asked about those improvements and others implemented after the Washington Navy Yard shooting last year, Defense Secretary Chuck Hagel admitted that "obviously… something is not working."

A preliminary investigation, however, found that Lopez showed "no sign of likely violence" to himself or others.

The cesspool of political opinion on Twitter, meanwhile, shows the incident already being used as a hook to push for gun control and to blame a "mental health crisis." The punditry usually isn't far behind.