A CNN Special Investigation drills down on the causes and the impact of the Fort Hood shootings, at 8 p.m. ET Saturday on CNN TV.

(CNN) -- Fort Hood, Texas, is -- for all intents and purposes -- a city. With as many as 30,000 residents, it has all the trappings of an American metropolis: malls, softball fields, subdivisions and as many as nine schools.

But in other ways, Fort Hood is like no American city. It is a transition point for troops who have served overseas, soldiers who have seen the worst that war has to offer and are returning to life at home.

At least 13 people were killed and 30 wounded in shootings on the post Thursday, officials said. The alleged gunman, identified as Maj. Nidal Malik Hasan, 39, was wounded.

Some of those killed or wounded were at the Readiness Center, a soldier's last stop before deployment, said Army Lt. Gen. Bob Cone. It is also one of the first places a soldier goes after returning from war.

Officials: Gunman opens fire at Fort Hood

Lt. Gen. Russel Honore, who served at Fort Hood in the late 1990s, said the nearly eight years of war in Afghanistan and Iraq have created difficulties for the U.S. armed forces.

"This is a very complex situation, a situation we have not dealt with in the Army before. We have never been at war this long before in modern history," he said. "And many of these soldiers have been deployed multiple times, so this has put a lot of stress on these soldiers and their families.

"One of the biggest things on re-entry that the Readiness Center does is to help those soldiers cope with being back home and dealing with the extremes of [post-traumatic stress disorder]," Honore said.

It is also where soldiers "do everything from finalizing your next of kin, inspect your immunization record, as well as make a will," he said.

Fort Hood is the largest U.S. military installation in the world by size, and on any given day, it is home to 25,000 to 30,000 people, according to an Army spokesman at the Pentagon. The post also houses the families of service members and other civilians.

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"Some of these soldiers have lost some of their closest friends, seen some of the horrific things associated with warfare including these roadside bombs," Honore said. "They've seen and experienced -- many of them -- some very horrific events."

Services and programs offered on the post range from helping troops who are leaving the armed services find employment or pursue education to helping soldiers deal with combat-related illnesses like post-traumatic stress disorder.

One such program, called the Warrior Stress Reset Program, is "designed to help address those common and normal reactions to war experiences," says a military Web site.

"It is well documented that participation in a major conflict ... has a way of leaving its mark on the psyche of our soldiers," the Web site reads.

The program lasts three weeks and provides counseling and treatment.

U.S. Sen. Kay Bailey Hutchison, R-Texas, said the post has a robust support system for families of deployed troops, which would help troops and civilians there handle Thursday's violence.

"The people who are there will surround the families and take care of them, the ones who have had loved ones who were killed," she said.

The Army's 1st Cavalry Division and elements of the 4th Infantry Division, as well as the 3rd Armored Cavalry Regiment and the 13th Corps Support Command, are based at Fort Hood.

Fort Hood measures about 340 square miles across and is approximately 160 miles south of Dallas/Fort Worth, Texas.

CNN's Barbara Starr, Adam Levine, Mike Mount and Chris Lawrence contributed to this report.