FORT HOOD, Texas -- A gunman killed three people before shooting himself to death in an attack Wednesday at Fort Hood, the same base that was the scene of the worst attack on a domestic U.S. military installation five years ago, officials said.

Lt. Gen. Mark Milley, head of the Army's III Corps at the Texas base, said the shooter was a veteran of combat in Iraq who had "mental health issues and was being treated for that.''

He said 16 people were wounded in the shooting attack. All those wounded and killed were military personnel, Milley said.

Milley said the shooter, whom he did not name, walked into a building on the base and opened fire, then got into a car, fired more shots and then went to another building shooting before he was engaged by responding military police. His body was recovered in a parking lot, he said.

"He died of a self-inflicted gunshot wound,'' Milley said.

The shooter used a .45 caliber semi-automatic weapon purchased recently in local area, Milley said. The shooter had not registered it with the base as required, he said.

"At this time there is no indication that this incident is related to terrorism, although we are not ruling anything out and the investigation continues,'' Milley said.

Specialist Brock Ruiz, a native of White Bear Lake, has been stationed at Fort Hood for three years and spoke to KARE 11 by phone Wednesday night. He says he was working on post when the shots rang out.

"I heard five to seven gunshots and then my sergeant called and said there was an active shooter," Ruiz said.

After Ruiz was told of the shooter he said he alerted his fellow soldiers nearby and then went into lockdown mode at the gymnasium on base.

After the lockdown ended Ruiz said he still felt unease about being on base day in and day out at Fort Hood.

"Some people here I just can't trust and I don't know what to think right now. It's crazy how we have two shootings in the past five years. They are soldiers. It's weird you know you work with people every day and you don't know who you can and can't trust here."