Check out more about Ranger Tillman's heroic sacrifice here.
U.S. military spokesman Lt. Col. Matthew Beevers said Saturday that Tillman was killed in a firefight on a road near Sperah, about 25 miles southwest of a U.S. base at Khost.
After coming under fire, Tillman's patrol got out of their vehicles and gave chase, moving toward the spot of the ambush. Beevers said the fighting was "sustained" and lasted 15-20 minutes. He was killed by enemy fire.
"That's real tough country," said CBS News Military Consultant Perry Smith. "It's very mountainous country, the government of Pakistan has never really been in control, there are a lot of tribal elements there. There are a lot of elements that support radical groups like al Qaeda. That's where there's been the greatest amount of combat activity over the last few months."