"World News with Charles Gibson" will air a special one-hour edition tonight focused on yesterday's massacre at Fort Hood.

Bob Woodruff, Terry Moran and Ryan Owens will report from Texas on the investigation, the victims and the heroic first responders. Brian Ross will report on what is known about the alleged shooter and his motives. Martha Raddatz and Bill Weir will contribute reporting on the impact on the US military.

In addition, Charlie Gibson will have an exclusive interview with Army Chief of Staff General George Casey Jr. and his wife, Sheila.

Last night on the broadcast, Gibson reflected on his time in the military, discussing the location of the massacre with correspondent John Quinones: "I go back to my time in the military, John. This is a processing center. And I remember, we used to line up to get shots and whatever just before we were about to do anything."