Ivan Lovez in full combat gear.

FORT HOOD, Texas – The soldier suspected of shooting dead three people before killing himself at the Fort Hood Army base in Texas was under psychiatric care but showed no signs of violence or suicidal tendencies, a U.S. official said on Thursday.

No motive was given for the rampage, which also left 16 wounded, in what was the second mass shooting in five years at one of the largest military bases in the United States, raising questions about security at such installations. Officials have so far ruled out terrorism.

The gunman, who had been treated for depression and anxiety, was yet to be officially named but security officials said preliminary information identified him as 34-year-old Ivan Lopez.

He is suspected of smuggling a recently purchased Smith & Wesson .45 caliber pistol on to the base, which was used in the shootings.

U.S. Army Secretary John McHugh said the soldier, who joined the service in 2008, had served two tours of duty abroad, including four months in Iraq in 2011. He had no direct involvement in combat and had not been wounded.

McHugh said the soldier and his wife were from Puerto Rico and that he had served in the Puerto Rican national guard before joining the U.S. Army.

Lopez served in the Puerto Rico National Guard from January, 1999 to 2009, in an infantry unit and as a band member, both military combat training assignments; He also had a six-month stint as part of an observation mission in the Sinai, Egypt, in 2006, Davis said.

At the modest blue-and-gray apartment building in Killeen where Ivan Lopez lived with his wife and 2-year-old daughter, American flags flew and “Welcome home” signs adorned the walls of a place favored by soldiers rotating through the base.

Military families at Fort Hood, a base still reeling from the 2009 attack when an Army psychiatrist killed 13 people and wounded 32 others, appeared shaken on Thursday.

There are about 45,000 soldiers and airmen assigned to the 335-square-mile (870-square-km) base along with nearly 10,000 civilian employees, according to Fort Hood.

Doctors at one local hospital said three shooting victims remained in critical condition.

The shooter, who arrived at Fort Hood in February, had “self-reported” a traumatic brain injury after returning from Iraq but was never wounded in action, said Fort Hood commanding officer Lieutenant General Mark Milley.

Before the shooting, he was being evaluated for PTSD, or post traumatic stress disorder.

It was not clear what spurred the gunman to enter two base buildings and open fire on fellow soldiers at about 4:00 p.m. local time on Wednesday.

The shooter walked into one of the unit buildings, opened fire, then got into a vehicle and fired from there. He then went into another building and opened fire again, until he was engaged by Fort Hood law enforcement officers, Milley said.

When confronted by a female military police officer in a parking lot, he shot himself with his semi-automatic weapon.

The incident is the third shooting at a military base in the United States in about six months that, along with a series of shootings in schools and malls, has sparked a national debate over gun violence.