It took the Army a month to change the record to show that Tillman, the Arizona Cardinals defensive back who gave up a $3.6 million contract to become an Army Ranger, was killed last April not by Afghan guerrillas but by his Ranger colleagues.
Even then, the statement by Lt. Gen. Philip R. Kensinger Jr., head of the Army's Special Operations Command, gave few specifics of the corporal's death and implied that he was trying to suppress enemy fire when he "probably died as a result of friendly fire."
The Washington Post on Sunday, in the first article of a two-part series written by Steve Coll, published what it described as the first full telling of how and why Tillman died. The newspaper said it had access to "dozens of witness statements, e-mails, investigation findings, logbooks, maps and photographs."
Tillman was based at Fort Lewis, Wash., part of the 2nd Battalion, 75th Ranger Regiment.
A series of mishaps and missteps began the chain of events that resulted in Tillman's death in eastern Afghanistan, the newspaper said. A Humvee broke down, which led to the splitting up of his platoon.
"There were six or seven turning points and one of the important ones was the decision to split the platoon that Pat was in to carry out two missions at the same time," Coll said on CBS News' Early Show. "This decision was made from a remote location over the objections from the platoon leader on the ground."
The segment of the platoon with Tillman, Serial One, passed through a canyon and was near its north rim. The other segment, Serial Two, changed its plans because of poor roads and followed the same route into the canyon. It came under fire from Afghan Taliban fighters.
Men in Serial One heard an explosion that preceded the attack, and Tillman and two other fire team leaders were ordered to head toward the attackers, the Post said. The canyon's walls prevented them from radioing their positions to their colleagues, just as Serial Two had not radioed its change in plans.
Tillman's group moved toward the north-south ridge to face the canyon, and Tillman took another Ranger and an Afghan ally down the slope.
"As they pulled alongside the ridge, the gunners poured an undisciplined barrage of hundreds of rounds into the area Tillman and other members of Serial One had taken up positions," the Post said Army investigators concluded. It said the gunner handling the platoon's only .50-caliber machine gun fired every round he had.
The first to die was the Afghan, whom the Americans in the canyon mistook for a Taliban fighter.
Under fire, Tillman and almost a dozen others on the ridge "shouted, they waved their arms, and they screamed some more," the Post said.
"Then Tillman 'came up with the idea to let a smoke grenade go.' As its thick smoke unfurled, 'This stopped the friendly contact for a few moments,'" a Ranger was quoted as saying.
Assuming the friendly fire had stopped, the Ranger said, he and his comrades emerged and talked with each other, the Post reported.
"Suddenly, he saw the attacking Humvee move into 'a better position to fire on us.' He heard a new machine gun burst and hit the ground, praying, as Pat Tillman fell," the Post reported.
The Ranger said Tillman had repeatedly screamed out his name and shouted for the shooting to stop, the Post said. He and others waved their arms, only attracting more fire. Tillman was shot repeatedly by rifles, finally succumbing to the machine gun.
The second part of the Post series, published on the newspaper's Web site Sunday night, tells of "a broader Army effort to manage the uncomfortable facts of Pat Tillman's death."
"Commemorations of Tillman's courage and sacrifice offered contrasting images of honorable service, undisturbed by questions about possible command or battlefield mistakes," the Post reported.
Sen. John McCain, R-Ariz., told the Post, "You may have at least a subconscious desire here to portray the situation in the best light, which may not have been totally justified."
"His mother said when they first revealed that it was friendly fire, that she thought initially, 'Well, accidents happen, I understand that," Coll told the Early Show. "But the more she learned about negligence and the cover-up that she saw at the Pentagon and the facts, the angrier she became. I think today she's looking for answers from the Pentagon."
Eventually, one member of Tillman's platoon received formal administrative charges; four others, including an officer, were discharged from the Rangers but not from the Army; and two additional officers were reprimanded, Lt. Col. Hans Bush, chief of public affairs for the Army Special Operations Command at Fort Bragg, told the Post.