Lucy Hamlin and her husband, Spc. Timothy Hamlin wait for permission to re-enter the Fort Hood military base, where they live, following a shooting on base, April 2, 2014, in Fort Hood, Texas.

Soldiers listen in the wings as Lt. Gen. Mark Milley address the media during a news conference at the main gate to Fort Hood, Wednesday, April 2, 2014, in Fort Hood, Texas. A soldier opened fire, April 2, 2014, on fellow service members at the military base, killing three people and wounding 16 before committing suicide, authorities said.

Lt. Gen. Mark Milley, the senior officer on base, speaks with the media outside of an entrance to the Fort Hood military base following a shooting that occurred inside, April 2, 2014, in Fort Hood, Texas. Four people were killed, including the gunman, and 16 were wounded in the attack, authorities said.

U.S. Secretary of Defense Chuck Hagel speaks about the shooting at Fort Hood during a news conference on the flight deck of the USS Anchorage (LPD-23), an amphibious transport dock ship, after a tour with his counterparts from Southeast Asia, April 2, 2014, at Joint Base Pearl Harbor-Hickam in Honolulu, Hawaii. Secretary Hagel is in Hawaii to host a meeting of defense ministers from the Association of Southeast Asian Nations (ASEAN). A MV-22 Osprey tiltrotor V/STOL aircraft is in the background.

Krystina Cassidy and Dianna Simpson attempt to make contact with their husbands who are stationed inside Fort Hood, while standing outside of the Bernie Beck Gate, April 2, 2014, in Fort Hood, Texas.

A shooting has been confirmed on the Fort Hood military base in Killeen, Texas, April 2, 2014.

A police officer checks drivers' IDs outside the main gate at Fort Hood, Texas, after a shooting at the Army base, April 2, 2014.

A military police officer stops a car at Fort Hood, Texas, after a shooting on the Army base, April 2, 2014.

A shooting has been confirmed on the Fort Hood military base in Killeen, Texas, April 2, 2014.

President Barack Obama pauses as he speaks about the shooting at Fort Hood, April 2, 2014, in Chicago.

A shooting has been confirmed on the Fort Hood military base in Killeen, Texas, April 2, 2014.

A shooting has been confirmed on the Fort Hood military base in Killeen, Texas, April 2, 2014.

Fort Hood has ordered everyone at the Texas Army base to "shelter in place," April 2, 2014.

The main gate at the U.S. Army post at Fort Hood, Texas is pictured in this undated photograph.