The Fort Hood shooting that killed three people plus the gunman, and wounded 16 others, remained a mystery Thursday as new details about suspected shooter Ivan Lopez began to emerge. But so far, at least, nothing in his background gave any indication that he was a ticking time bomb just waiting to explode into a homicidal rampage.

But some information surfaced that could shed light on the mass shooting. Among other details, the Army revealed that the soldier suspected in the Fort Hood shooting was prescribed the sleeping drug Ambien, and had once reported a brain injury, though the military has no record that he was ever wounded.

‘Heroic’ Military Policewoman Confronting Suspect When He Killed Himself

The Army has still not officially identified the Fort Hood shooting suspect, but Texas congressman Michael McCaul named him as Lopez. The gunman took his own life as a military policewoman confronted him Wednesday.

“It was clearly heroic, what she did at that moment in time,” said Fort Hood commanding officer Lieutenant General Mark Milley.

Though what sparked the Fort Hood shooting is still a puzzle, the Army has dismissed the possibility that the shooting rampage was some kind of terrorist attack.

Fort Hood Shooting Suspect May Have Had Unspecified Brain Injury

The army said that though he had served two tours of duty abroad, including four months in Iraq in 2011, Lopez was never involved in combat and was not wounded. However, Lopez himself reported to the Army that while in Iraq he suffered a “traumatic brain injury,” which according to the Army he had “self-diagnosed.”

The nature of that injury and how Lopez might have incurred it were not mentioned by Milley in a press briefing late Wednesday.

Ambien Sleeping Drug Linked To Previous Homicides

Lopez was also prescribed the popular sleeping drug Ambien — sometimes known by the generic name Zolpidem — according to U.S. Army Secretary John McHugh, who said that the Fort Hood shooting suspect was undergoing treatment for some mental health issues, including sleep disturbance as well as depression and anxiety.

But nothing in his symptoms showed clear warning signs of suicidal or homicidal behavior on the horizon, McHugh said, adding that the Fort Hood gunman’s background revealed no ties or connections to extremist groups or terrorism.

However, in at least two cases, Zolpidem has been linked to homicides, according to a 2012 National Institutes of Health report. In both of those cases, individuals with no history of “aggressive behavior” killed their spouses after having ingested at least 10 milligrams of the widely-used prescription sleeping aid. Both claimed amnesia after the killings. Both killers also had at least some history of prior psychiatric disorders, as did Lopez.

Facebook Page Uncovered That May Have Been Created By Shooting Suspect

ABC News uncovered a Facebook page that it said apparently belonged to Ivan Lopez, though the Facebook page was created in the name “Ivan Slipknot,” in seeming tribute to the heavy metal band Slipknot.

A photo of a man that ABC identifies as Lopez, from the “Ivan Slipknot” page, is above.

Though the page appeared to have been disabled by Thursday morning, according to the ABC report, one photo on the page showed the man who was apparently the Fort Hood shooting suspect in full combat gear with a caption reading in part, “memories of Fallujah, Iraq 2011.”

The Army did not say whether the Fort Hood shooting suspect had been stationed in Fallujah, an Iraqi city which was the site of one of the Iraq War’s bloodiest battles in 2004.

Image: Ivan Slipknot Facebook via ABC News