-Tillman's platoon had nearly run out of vital supplies, according to one of the shooters. They were down to the water in their CamelBak drinking pouches, and were forced to buy a goat from a local vendor. Delayed supply flights contributed to the hunger, fatigue and possibly misjudgments by platoon members.

-A key commander in the events that led to Tillman's death both was reprimanded for his role and meted out punishments to those who fired, raising questions of conflict of interest.

-A field hospital report says someone tried to jump-start Tillman's heart with CPR hours after his head had been partly blown off and his corpse wrapped in a poncho; key evidence including Tillman's body armor and uniform was burned.

-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 has 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 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:

Who fired the shots that killed Pat Tillman, and why?

Who insisted Tillman's platoon split and travel through dangerous territory in daylight, against its own policy? Who let the command slip away and chaos engulf the unit?

And perhaps most of all: Was a crime committed?

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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.

Impatience was rising at the tactical operations center at Forward Operating Base Salerno, near Khowst, Afghanistan, where officers coordinated the movements of several platoons. Led by then-Maj. David Hodne, the so-called Cross-Functional Team worked at a U-shaped table inside a 20-by-30-foot tent with a projection screen and a satellite radio.

(Hodne, now a lieutenant colonel and executive officer for the 75th Ranger Regiment, declined to be interviewed on the record by the AP - as did nearly every person involved in the incident.)

When the Humvee broke down, the Black Sheep were nearing the end of their assignment; all that was left was to "turn one last stone and then get out,'' Hodne would testify. The unit was then to head for Manah, a small village where it would spend the night.

The commanders had already given the Black Sheep an extra day to get into its grid zones. High-ranking commanders were "pushing us pretty hard to keep moving,'' said Hodne.

"We had better not have any more delays due to this vehicle,'' he told his subordinates.

At the operations center, the Black Sheep's company commander, then-Capt. William C. "Satch'' Saunders, was feeling the heat to get the platoon moving.

"We wanted to make sure we had a force staged to confirm or deny any enemy presence in Manah the next day, so we would not get ourselves too far behind setting ourselves up for our next series of operations,'' he recalled later to an investigator.

The order came down to split the platoon in two to speed its progress.

Saunders initially told investigators that Hodne had issued the order, but later, after he was given immunity from prosecution, he acknowledged it was his decision alone.

Hodne later said he was in the dark - "I felt like the village idiot because I had no idea what they were doing,'' he recalled. The decision was foolhardy, he said. Divided in two, "they didn't have enough combat power to do that mission'' of clearing Manah, he testified. (Other commanders have insisted that splitting the platoon was perfectly safe and a common practice.)

One thing is clear: The order sparked a flurry of activity by the Black Sheep.

One of the gunners who shot Tillman said his unit didn't even have time to look at a map before getting back on the road.

"We were rushed to conduct an operation that had such flaws,'' said Alders. "Which in the end would prove to be fatal.''

"If anything, this sense of urgency was as deadly to Tillman as the bullet that cut his life short,'' Alders wrote in a lengthy statement protesting his expulsion from the Rangers. "We could have conducted the search at night like we did on the follow-up operations or the next morning like we ended up doing anyway. Why, I ask, why?''

An investigator, Brig. Gen. Gary M. Jones, would later agree that an "artificial sense of urgency'' to keep Tillman's platoon moving was a crucial factor in his death: "There was no specific intelligence that made the movement to Manah before nightfall imperative.''

An officer involved in the incident told AP there was, however, general intelligence of insurgent activity in this region, historically a Taliban hotbed.

That suspicion would be confirmed when the Black Sheep drove through a narrow canyon, its walls towering about 500 feet, and came under fire from enemy Afghans. Chaos broke out and communications broke down.

After the platoon split, the second section of the convoy roared out of the canyon, into an open valley and straight at their comrades a few minutes ahead. A Humvee packed with pumped-up Rangers opened fire, killing the friendly Afghan and Tillman, though he desperately sought to be recognized.

Later, at least one of the same Rangers turned his guns on a village where witnesses say civilian women and children had gathered. The shooters raked it with fire, the American witnesses said; they wounded two additional fellow Rangers, including their own platoon leader.

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Had it happened in the United States, police would have quickly cordoned off the area with "crime scene'' tape and determined whether a law had been broken.

Instead, the investigations into Tillman's death have cascaded, one after another, for the past 30 months.

For Mary Tillman, getting to the bottom of her son's death is more than a personal quest.

"This isn't just about our son,'' she said. "It's about holding the military accountable. Finding out what happened to Pat is ultimately going to be important in finding out what happened to other soldiers.''

In the days after the shootings, the first officer appointed to investigate, then-Capt. Richard Scott, interviewed all four shooters, their driver, and many others who were there. He concluded within a week that the gunmen demonstrated "gross negligence'' and recommended further investigation.

"It could involve some Rangers that could be charged'' with a crime, Scott told a superior later.

Then-Lt. Col. Jeffrey Bailey - the battalion commander who oversaw Tillman's platoon - later assured Tillman's family that those responsible would be punished as harshly as possible.

But no one was ever court-martialed; staff lawyers advised senior Army commanders reviewing the incident that there was no legal basis for it.

Instead, the Army punished seven people; four soldiers received relatively minor punishments known as Article 15s under military law, with no court proceedings. These four ranged from written reprimands to expulsion from the Rangers. One, Baker, had his pay reduced and was effectively forced out of the Army. The three other soldiers received administrative reprimands.

Scott's report circulated briefly among a small corps of high-ranking officers.

Then, it disappeared.

Some of Tillman's relatives think the Army buried the report because its findings were too explosive. Army officials refused to provide a copy to the AP, saying no materials related to the investigation could be released.

The commander of Tillman's 75th Ranger Regiment, then-Col. James C. Nixon, wasn't satisfied with Scott's investigation, which he said focused too heavily on precombat inspections and procedures rather than on what had happened.

Scott "made some conclusions in the document that weren't validated by facts'' as described by the participants, Nixon would tell later investigators.

Nixon assigned his top aide, Lt. Col. Ralph Kauzlarich, to lead what became the second investigation. Kauzlarich harshly criticized Baker and the men on his truck.

Among other things, Baker should have known that at least two of his subordinates had never been in a firefight, and should have closely supervised where they shot.

"His failure to do so resulted in deaths of Cpl. Tillman and the AMF soldier, and the serious wounding of two other (Rangers),'' Kauzlarich concluded. "While a great deal of discretion should be granted to a leader who is making difficult judgments in the heat of combat, the command also has a responsibility to hold its leaders accountable when that judgment is so wanton or poor that it places the lives of other men at risk.''

Still, the Tillman family complained that questions remained: Who killed Tillman? Why did they fire? Were the punishments stiff enough?

"I don't think that punishment fit their actions out there in the field,'' said Kevin Tillman, who was with his brother the day Pat was killed but was several minutes behind him in the trailing element of a convoy and saw nothing.

"They were not inquiring, identifying, engaging (targets). They weren't doing their job as a soldier,'' he told an investigator. "You have an obligation as a soldier to, you know, do certain things, and just shooting isn't one of your responsibilities. You know, it has to be a known, likely suspect.''

And so, in November 2004, acting Army Secretary Les Brownlee ordered up yet another investigation, by Jones.

The result was 2,100 pages of transcripts and detailed descriptions of the incident, but no new charges or punishments. The report, completed Jan. 10, 2005, was provided - with many portions blacked out or removed entirely - to the Tillman family. It has not been released to the public; the family found it wanting.

Pressed anew by the Tillmans, the Pentagon inspector general announced a review of the investigations in August 2005. And in March 2006, they launched a new criminal probe into the actions of the men who shot at Tillman.

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The veteran Pentagon official who is overseeing these latest inquiries, acting Defense Department Inspector General Thomas Gimble, has called the Tillman probe the toughest case he has ever seen, according to people he recently briefed.

Investigators are looking at who pulled the triggers and fired at Tillman; they are also looking at the officers who pressured the platoon to move through a region with a history of ambushes; the soldiers who burned Tillman's uniform and body armor afterward; and at everyone in the chain of command who deliberately kept the circumstances of Tillman's death from the family for more than a month.

Military investigators under Gimble's direction this year visited the rugged valley in eastern Afghanistan where Tillman was killed. It was a risky trip; the region is even more dangerous today than it was in 2004.

According to one person briefed by investigators, the contingent included at least two soldiers who were there the day of the incident - Staff Sgt. Matthew Weeks, a squad leader who was up the hill from Tillman when he was shot, and the driver of the GMV that carried the Rangers who shot Tillman, Staff Sgt. Kellett Sayre.

When the current inquiry began, the Pentagon projected it would be completed by September 2006. Now Gimble and the Army's Criminal Investigation Command, known as CID, are aiming to finish their work by December, say lawmakers and other officials briefed by Gimble.

CID is probing everything up to and including Tillman's shooting. The inspector general's office itself has a half-dozen investigators researching everything that happened afterward, including allegations of a coverup.

The investigators have taken sworn testimony from about 70 people, some of whom said they were questioned for more than six hours. But Gimble said investigators have been hindered by a failure to locate key witnesses, even some who are still in the active military.

Moreover, those who are now out of the Army, including three of the four shooters, can't be court-martialed. They could be charged in the civilian justice system by a U.S. attorney, but such a step would be highly unusual.

The law that allows it, the Military Extraterritorial Jurisdiction Act, has been invoked fewer than a half-dozen times since its enactment in 2000, said Scott Silliman, executive director of Duke Law School's Center on Law, Ethics and National Security and a high-ranking Air Force lawyer until his retirement in 1993.

The investigation, Gimble has said, is also complicated because of "numerous missteps'' by the three previous investigators, particularly their failure to follow standards for handling evidence.

Gimble promised lawmakers in a series of briefings this fall that his investigation "will bring all to light.'' He has committed to releasing his detailed findings to key legislators, Pentagon officials and the Tillman family, as well as a synopsis to the general public, congressional aides said.

Gimble declined an AP request for an interview.

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To date, a total of seven soldiers have been disciplined in Tillman's death.

Bailey, the 2nd Ranger Battalion commander who was camped out about two miles down the road with another unit the night Tillman died, surveyed the shooting scene hours after it occurred.

"I don't think there was any criminal act,'' he said. "It was a fratricide based upon a lot of contributing factors, confusion,'' he testified to an investigator in late 2004.

Some high-ranking officers, including Bailey, believe a lack of control in the field was to blame - starting with the platoon leader and including the soldiers who didn't identify their targets.

Bailey, who approved punishments for several of the soldiers, said he disagreed with the platoon's protests that they were "doing what we asked them to do under some very difficult circumstances, and that there were mistakes made but they weren't negligent mistakes.''

He also testified that "three gunners were, to varying degrees, culpable in what had happened out there.'' And he said he wanted a fourth soldier involved - the squad leader, Baker - "out of the military.''

Baker soon left the Army.

As for others involved:

-The three other shooters - Ashpole, Alders and Elliott - remained in the service initially but Elliott and Ashpole have since left. Elliott struck a deal with authorities; in exchange for his testimony to investigator Jones, the Army gave him immunity from prosecution "in any criminal proceedings.''

-The platoon leader, Lt. David Uthlaut, was later bumped down from the Rangers to the regular Army for failing to prepare his men prior to the shootings, according to Bailey.

"They didn't do communications checks. They didn't check out their equipment. So they'd been there 24 hours,'' Bailey testified. "For example, some of the weapons systems weren't even loaded with ammunition. Many of the soldiers didn't know where they were going. They didn't have contingency plans.''

A non-commissioned officer on the ground that day, however, testified that the unit carried out required communications checks.

Uthlaut was also wounded by fellow Rangers in the incident. He was awarded the Purple Heart and later promoted to captain.

-Saunders, the company commander, was given the authority to punish three soldiers - even though he himself was reprimanded for his own poor leadership. Both Saunders and Hodne received formal written reprimands for failing to "provide adequate command and control'' of subordinate units - administrative punishments lighter than the Article 15s handed down to the soldiers who shot at Tillman. This obviously hasn't hurt Hodne's career; he has since been promoted.

"I thought it was (the commanders') fault, or part of their fault that we were even in this situation, when they're telling us to split up,'' said Ashpole.

Some lawmakers have warned that if this probe does not clear up all questions on Tillman's death, they may press for congressional hearings. Others have said Congress could call for an independent panel of retired military officers and other experts to conduct an outside probe.

Rep. Mike Honda, a Democrat who represents the San Jose district where Tillman's family lives, has pressed the Pentagon for answers on the status of its investigations.

"I'm very impatient and at times cynical,'' Honda said. But, he said, the honor of the military - and the confidence of the public in the military and the government - are at stake.

"So if we pursue the truth and wait for it,'' he said, "it may be worthwhile.''