They walked the landscape with surviving witnesses. They found a rock stained with the blood of the victim. They re-enacted the killings — here the U.S. Army Rangers swept through the canyon in their Humvee, blasting away; here the doomed man waved his arms, pleading for recognition as a friend, not an enemy.
"Cease fire, friendlies, I am Pat (expletive) Tillman, damn it!" he shouted, again and again.
The latest inquiry into Tillman's death by friendly fire should end next month; authorities have said they intend to release to the public only a synopsis of their report. But The Associated Press has combed through the results of more than two years of investigations — reviewed thousands of pages of internal Army documents, interviewed dozens of people familiar with the case — and uncovered some startling findings.
One of the four shooters, Staff Sgt. Trevor Alders, had recently had PRK laser eye surgery. Although he could see two sets of hands "straight up," his vision was "hazy," he said. In the absence of "friendly identifying signals," he assumed Tillman and an allied Afghan who also was killed were enemy.
Another, Spc. Steve Elliott, said he was "excited" by the sight of rifles, muzzle flashes and "shapes." A third, Spc. Stephen Ashpole, said he saw two figures, and just aimed where everyone else was shooting.
Squad leader Sgt. Greg Baker had 20-20 eyesight, but claimed he had "tunnel vision." Amid the chaos and pumping adrenaline, Baker said he hammered what he thought was the enemy but was actually the allied Afghan fighter next to Tillman who was trying to give the Americans cover: "I zoned in on him because I could see the AK-47. I focused only on him."
All four failed to identify their targets before firing, a direct violation of the fire discipline techniques drilled into every soldier.
Investigators have been stymied because some of those involved now have lawyers and refused to cooperate, and other soldiers who were at the scene couldn't be located.
Three of the four shooters are now out of the Army, and essentially beyond the reach of military justice.
Taken together, these findings raise more questions than they answer, in a case that already had veered from suggestions that it all was a result of the "fog of war" to insinuations that criminal acts were to blame.
The Pentagon's failure to reveal for more than a month that Tillman was killed by friendly fire have raised suspicions of a coverup. To Tillman's family, there is little doubt that his death was more than an innocent mistake.
One investigator told the Tillmans that it hadn't been ruled out that Tillman was shot by an American sniper or deliberately murdered by his own men — though he also gave no indication the evidence pointed that way.
"I will not assume his death was accidental or 'fog of war,"' said his father, Pat Tillman Sr. "I want to know what happened, and they've clouded that so badly we may never know."
And so, almost two years after three bullets through the forehead killed the star defensive back — a man who President Bush would call "an inspiration on and off the football field" — the fourth investigation began.
This time, the investigators are supposed to think like prosecutors:
The long and complicated story of Pat Tillman's death and the investigations it spawned began five years ago, in the smoking ruins of the World Trade Center.
"It is a proud and patriotic thing you are doing," Defense Secretary Donald H. Rumsfeld wrote to Tillman in 2002, after Tillman — shocked and outraged by the Sept. 11 attacks — turned down a multimillion-dollar contract with the Arizona Cardinals to join the elite Army Rangers.
The San Jose, Calif. native enlisted with his brother Kevin, who gave up his own chance to play professional baseball. The Tillmans were deployed to Iraq in 2003, then sent to Afghanistan.
The mission of their "Black Sheep" platoon in April 2004 sounded straightforward: Divide a region along the Pakistan border into zones, then check each grid for insurgents and weapons. They were to clear two zones and then move deeper into Afghanistan.
But a broken-down Humvee known as a Ground Mobility Vehicle, or GMV, stalled the unit on an isolated road. A mechanic couldn't fix it, and a fuel pump flown in on a helicopter didn't help.
Hours passed. Enemy fighters watched invisibly, plotting their ambush.
Tillman's platoon must have presented an inviting target. There were 39 men — including six allied Afghan fighters trained by the CIA — and about a dozen vehicles.