FORT HOOD, Texas — A Nederland soldier who was stationed at Fort Hood in 2005 watched TV news and the Internet for information about the grisly tragedy unfolding at his former base on Thursday.

The violence began when a military mental health doctor facing deployment overseas opened fire at the Fort Hood Army post, setting off on a rampage that killed 11 other people and left 31 wounded.

Authorities killed the gunman, and the violence was believed to be the worst mass shooting in history at a U.S. military base.

The shooting began around 1:30 p.m., when shots were fired at the base’s Soldier Readiness Center, where soldiers who are about to be deployed or who are returning undergo medical screening, said Lt. Gen. Bob Cone at Fort Hood.

Jeremy Seiley of Nederland heard of the tragedy from his wife’s friends, he said. Media video and photographs showed buildings Seiley was familiar with.

“My barracks were just a couple of blocks from the place. I was kind of shocked,” he said. “Honestly, it’s the last thing I thought would happen.”

Seiley expressed sympathy for the families involved.

“My heart goes out to them,” he said.

Back in Washington, D.C., President Barack Obama called the shooting “a horrific outburst of violence.” He said it is a tragedy to lose a soldier overseas and even more horrifying when they come under fire at an Army base on American soil.

“We will make sure that we get answers to every single question about this horrible incident,” the commander in chief said in Washington. “We are going to stay on this.”

A law enforcement official identified the shooting suspect as Army Maj. Nidal Malik Hasan. The official spoke on condition of anonymity because he was not authorized to discuss the case publicly.

It was unclear what the motive was, though it appeared he was upset about a scheduled deployment. U.S. Sen. Kay Bailey Hutchison said the Army major was about to deploy overseas, though it was unclear if he was headed to Iraq or Afghanistan and when he was scheduled to leave. Hutchison said she was told about the upcoming deployment by generals based at Fort Hood.

Retired Army Col. Terry Lee told Fox News that he worked with Hasan, who had hoped Obama would pull troops out of Afghanistan and Iraq. Lee said Hasan got into frequent arguments with others in the military who supported the wars, and had tried hard to prevent his pending deployment.

Military officials say Hasan, 39, was a psychiatrist at Walter Reed Army Medical Center for six years before being transferred to the Texas base in July. The officials, who had access to Hasan’s military record, said he received a poor performance evaluation while at Walter Reed. The officials spoke on condition of anonymity because military records are confidential.

The Virginia-born soldier was single with no children. He graduated from Virginia Tech, where he was a member of the ROTC and earned a bachelor’s degree in biochemistry in 1997. He received his medical degree from the military’s Uniformed Services University of the Health Sciences in Bethesda, Md., in 2001. At Walter Reed, he did his internship, residency and a fellowship.