William M. Welch

USA TODAY

A soldier killed three people and wounded 16 others before shooting himself to death Wednesday at Fort Hood, the same Texas base that was the scene of the worst attack on a domestic U.S. military installation five years ago, officials said.

U.S. Rep. Michael McCaul of Texas told reporters that the suspected shooter is Spc. Ivan Lopez.

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

"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.

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

Milley said the shooter walked into a building on the post and opened fire around 4 p.m., 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 suspect used a .45-caliber semi-automatic weapon purchased recently in the local area, Milley said. The suspect had not registered it with the post as required, he said.

Milley said the suspect was undergoing "psychiatric treatment for depression and anxiety and a variety of other psychological" problems. He said the soldier was undergoing a diagnosis process to determine if he had post-traumatic stress disorder, but had not been diagnosed with it.

Milley said the gunman was not wounded in action, according to military records, though he said there are reports the soldier "self-diagnosed" a traumatic brain injury from Iraq.

"We're heartbroken something like this might have happened again,'' President Obama said in Chicago, after being briefed on the events.

The post was locked down and personnel directed to "shelter in place.'' The lockdown was lifted Wednesday night.

Glen Couchman, chief medical officer at Scott and White Hospital in Temple, said the first four people admitted there had gunshots to chest, abdomen, neck and extremities and that their conditions range from stable to "quite critical."

Fort Hood was the post where 13 died and more than 30 were wounded in the deadliest domestic military attack in U.S. history.

Army psychiatrist Nidal Hasan was convicted and sentenced to death last year in the Nov. 5, 2009, attack on his fellow soldiers as they waited inside a crowded building at Fort Hood. Soldiers there were waiting to get vaccines and routine paperwork after recently returning from deployments or while preparing to go to Afghanistan and Iraq.

Defense Secretary Chuck Hagel, speaking to reporters while in Honolulu to host a conference of Southeast Asian defense leaders, called the shootings a "terrible tragedy." Asked about security improvements in the wake of other shootings at U.S. military bases, Hagel said, "Obviously when we have these kinds of tragedies on our bases, something's not working."

Contributing: Jim Michaels, Tom Vanden Brook, Yamiche Alcindor; KVUE-TV; Associated Press