But as Katie Couric reports, that story didn't hold up. He had really been killed by friendly fire, shot accidentally by his fellow soldiers.
For the past four years, his family, led by his mother Mary, has been searching for answers about what really happened, beginning the day she heard the news from Pat Tillman's wife Marie.
"And she answered the phone just the way she always does. Her voice sounded just the same. And I just sort of breathed a sigh of relief, like, 'Oh, you know, everything's fine.' And I said, 'What's wrong, what's wrong?' And she said, 'He's dead.' And I said, 'Who's dead?' And she said, 'Pat's dead.' Within minutes of that, the Army had sent a soldier, a young, female soldier, to come tell me about what had happened," Mary Tillman remembers.
Asked what the soldier told her, Tillman says, "She said that he was shot getting out of a vehicle. He was shot in the head getting out of a vehicle. And that's basically all she knew."
Eleven days after his death, Pat Tillman's family held a memorial service in their hometown of San Jose, Calif.
At that time, Tillman's family was led to believe that he was killed by the enemy, which was reinforced when the Army awarded him a Silver Star for his "gallantry in action against an armed enemy." They were told his convoy had been ambushed and he had charged up a hill, forcing the enemy to withdraw and saving the lives of his fellow Rangers.
"Was there any solace in the story the military told you about how courageous Pat had been?" Couric asks.
"Well, of course. But what's interesting is the story itself seemed so contrived, even then, even before he knew that it was contrived. It had this contrived feel to it," Tillman says.
Asked why, she says, "Well, you know, the soldier, you know, running up the ridge line, firing at the enemy. You know, saving his men. It did sound kind of like a John Wayne movie."
Then, about a month later there was a stunning announcement: the Army had been investigating his death and determined that Tillman was killed by his own men.
Asked how long she thinks it took the Army to realize her son had been killed by friendly fire, Tillman says, "Oh, they knew immediately. It was pretty evident right away. All the other soldiers on the ridge line suspected that that's exactly what happened."
Tillman says it took the Army five weeks to tell her. "Even the time lapse is not what is so disturbing to us. If they didn't tell us right away exactly what happened, I mean, it would seem to me that because of the clandestine nature of the Rangers, they could've easily said, 'Well, this is, you know, we can't really divulge this,'" she says.
"It's under investigation," Couric remarks.
"It's under investigation. You know, they could've said anything. But they made up a story," Tillman says.
"Made up" a story, Mary contends, because when her son had left behind his football career to join the Army Rangers, he'd become one of the most high-profile soldiers in the U.S. military. He'd signed up to fight al Qaeda following Sept. 11, and talked about the importance of service one day after the attacks.
"You know, my great-grandfather was at Pearl Harbor, and a lot of my family has given up, has gone and fought in wars, and I really haven't done a damn thing, as far as laying myself on the line like that. And so I have a great deal of appreciation for those who have," Pat Tillman said at the time.
After her son's death, Mary Tillman says she never felt like she got the straight story. And so the divorced middle school teacher launched her own investigation. Combing through Army documents, she found inconsistencies in the official military account. Tillman's brother Kevin was in the back of the convoy, but hadn't seen what happened. So she tracked down some other Rangers who were there that day.
While there is some disagreement about the details of what happened the day Tillman was killed, the Rangers 60 Minutes spoke with said it began when their commanders made a critical error, splitting their convoy into two groups as they moved through Taliban territory.
"That was a pretty scary situation you were driving into and you knew it?" Couric asks.
"And we knew it, absolutely," Russell Baer replies.
"We can all identify that feeling as we drove into that canyon and we knew this is not a good spot," Brad Jacobson adds.