WASHINGTON — A soldier killed three fellow soldiers and wounded 16 more before killing himself at Fort Hood, Texas, officials said tonight.

There is no evidence that the incident is related to terrorism, said Army Lt. Gen. Mark A. Milley, the commander of 3rd Corps and Fort Hood.

"We are not ruling anything out, and the investigation continues," the general said during a late-night news conference. "Our focus now is to focus on the families of the injured, and focus on the families of the killed [to] ensure they have the best care and counseling available."

The soldier used a recently purchased .45-caliber pistol and first fired on personnel in the 1st Medical Brigade at about 4 p.m. CST before moving on to the 49th Transportation Battalion.

A military policewoman confronted him in a parking lot, where he drew his pistol and killed himself. Milley called the MP's actions heroic.

The soldier — whose name is withheld until his next of kin are notified — had some behavioral health and mental health issues and was being evaluated for post-traumatic stress, Milley said.

"When we have these kinds of tragedies on our bases, something is not working," Defense Secretary Chuck Hagel said during a news conference in Hawaii, where he has been attending a conference of Pacific-nation defense ministers and visiting U.S. forces.

In a written statement issued by the Pentagon, Hagel stressed that nothing is more important to the department than the safety and well-being of service members and their families. "I am grateful to all the first responders who rushed to the scene," he said. "We will closely monitor the situation at Fort Hood and stay informed by what investigators and law enforcement personnel learn about the shooting."

President Barack Obama also is following the situation closely. In an appearance in Chicago, the president said DOD, federal and state officials will work together to find out what happened and why.

Obama said the shooting reopens the pain of the shootings at Fort Hood five years ago. "We know these families," he said. "We know their incredible service to our country and the sacrifices that they make. Obviously, our thoughts and prayers are with the entire community."

The chairman of the Joint Chiefs of Staff said the thoughts and prayers of the greater military community are with those at Fort Hood. "Many questions remain, and our focus is on supporting the victims and their families," Army Gen. Martin E. Dempsey said in a statement released at the Pentagon. "This is a community that has faced and overcome crises with resilience and strength."

Personnel on the base were ordered to shelter in place, and the order was lifted about 10 p.m. EST.