Ever since he was a kid, Kevin Tillman was never far from his big brother, Pat.
On April 22, 2002, both were Army Rangers, and Spc. Kevin Tillman pulled up to the scene of his brother's shooting manning a turret gun on a Humvee just minutes after Pat Tillman was slain in a hail of friendly fire.
"What's going on?" Kevin Tillman asked his fellow Rangers, having heard the shooting as his vehicle struggled through a rocky, narrow Afghan canyon that kept its speed below 5 mph.
When a Ranger asked the driver of Kevin Tillman's vehicle if the crew had a litter for carrying casualties, Tillman asked, "Who got hit?" He was told it was an Afghan.
An Afghan had been killed alongside Pat Tillman.
Watch the story tonight on "Nightline" at 11:35 p.m. ET and watch best-selling author Jon Krakauer's first live interview about his new book "Where Men Win Glory: The Odyssey of Pat Tillman" Monday on "Good Morning America."
While standing guard, Kevin Tillman said he became uneasy because his brother's booming voice and laugh was missing from the scene.
"I started to get a little weird feeling, you know, because my brother's a pretty loud-type guy," Kevin Tillman told an investigator who looked into the friendly fire incident.
"Where's Pat?" he began asking his colleagues.
"He asked me three times," said Sgt. Jason Parsons.
Finally, the sergeant told Kevin Tillman that his brother was dead.
Tillman was silent for a few minutes. Then he howled and cursed in grief and rage. The platoon's doctor took his gun away.
But even though it was apparent to most of the platoon members who were present for the shooting's aftermath that Pat Tillman had been killed by a fellow Ranger, no one told Kevin Tillman.
Later that night, Kevin Tillman was summoned by Maj. David Hodne as Tillman got off a helicopter that evacuated him from the shooting site to offer Tillman a chance to be counseled by a chaplain. Tillman declined the offer, and asked Hodne for a promise instead.
"He asked me to promise to exact revenge on the ambushers," Hodne testified to an Army investigator, according to Krakauer.
Hodne said he promised that whoever killed Pat Tillman would pay dearly, a vow that Krakauer said was the Army's first lie to the Tillman family.
Kevin Tillman was born 14 months after Pat Tillman, and because his older brother pronounced "Kevin" as "Nubbin," the name Nubbin or Nub has stuck with Kevin throughout his life.
While Pat Tillman played professional football, Kevin Tillman was signed by the Cleveland Indians and played professional baseball in the Indians' minor league system.
When Pat Tillman decided to enlist, his wife Marie remembered telling him, "It's not fair to Kevin, in some ways -- because you know he's going to come with you."
The two Tillmans went through the Army's boot camp together and later the grueling Ranger school. They were both deployed to Iraq and then sent to Afghanistan together. In their off hours, Kevin Tillman lived with Pat and Marie Tillman.
Kevin Tillman accompanied his brother's body back to the States, but on the day he left he asked nearly every Ranger he met to find the notebook that his brother was carrying to jot down his thoughts. All assured Kevin Tillman they would look for it.
Instead, the notebook was burned along with Pat Tillman's uniform and body armor.