Saturday, May 27, 2006; Posted: 7:24 p.m. EDT (23:24 GMT)

At his memorial service, mourners remembered the 27-year-old Tillman as an inspiration to thousands of Americans. California's first lady Maria Shriver was among those supporting the family, recalling how much Tillman gave up to fight for his country in Afghanistan. (Watch a CNN animation of how Tillman met his death -- 3:22)

"Pat had it all," she said. "Intelligence, movie star good looks, a loving wife, athletic prowess, fame. A lucrative and promising career. Who among us could walk away from riches and a job we love?"

Tillman did.

The former safety for the Arizona Cardinals gave up a multimillion dollar pro football deal the day after the terror attacks of September 11, 2001, to enlist as an elite Army Ranger. He explained his decision in a rare interview just before he went into the Army.

"My great-grandfather was at Pearl Harbor," he said. "And a lot of my family has given up -- you know, has -- 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."

But Tillman's devotion to "duty, honor, country" ended with his death in a desolate section of Afghanistan.

And it wasn't until 26 days after the memorial service -- more than a month after his death -- that the Army would publicly acknowledge what the Rangers who were with him in combat knew almost right away: Tillman died in "friendly fire." He was hit in the head by three bullets fired by U.S. soldiers who say they mistook him for the enemy. (Watch how Tillman's death is being pieced together -- 13:46)

Much -- but not all -- of the story of what went wrong that April day in 2004 can be found in thousands of Army documents obtained by CNN. And while the heavily blacked-out documents provide some answers -- they also raise substantial questions that three separate Army investigations have failed to resolve.

'Friendlies! Cease fire!'

Tillman's platoon was on a mission in eastern Afghanistan, along the Pakistan border. His platoon was trying to flush out enemy Taliban or al Qaeda fighters. The platoon's problems began with a broken-down Humvee, which had to be towed by a local truck and was slowing the platoon.

The platoon was split into two groups, on orders of a commander at a base far away, according to Army documents. The split was ordered over the objections of the platoon leader. But the base commander was concerned that the broken vehicle was delaying the mission.

Cpl. Pat Tillman was with the first group that pressed on, moving safely through a deep canyon and arriving at a small village. The second group -- with the Humvee in tow -- included Tillman's younger brother Kevin, who enlisted with Pat after September 11.

That second convoy followed a different route but found the terrain too rugged.

So they backtracked and followed the first group deep into the narrow canyon. Although they were just a half hour back, the first group was unaware the second group was coming up behind them.

In the canyon, the second group was ambushed from above by enemy fighters. To add to the confusion, in the deep canyon, the two groups lost radio contact.

Tillman and I were yelling 'Stop! Stop! Friendlies! Friendlies! Cease fire!' But they couldn't hear us.

But Pat Tillman's group heard the gunfire back in the canyon and turned back to help. Tillman -- as described in his Silver Star citation -- showed great courage under fire in leading a small rifle team -- including an Afghan soldier -- to the top of a ridge to engage the enemy.

Down below, a Humvee armed with a .50-caliber machine gun and four soldiers with other weapons pulled out from behind the truck and broken Humvee.

As they emerged from the canyon, the soldiers in the vehicle were firing with an abandon that one Army investigator said demonstrated gross negligence. The soldiers later said that they thought the enemy was all around them. As they fired in all directions, they began hitting U.S. troops. The platoon leader was hit in the face and another soldier shot in the leg.

From Tillman's position up on the ridge came anguished cries of alarm. First, the Afghan soldier was shot and killed by the soldiers in the Ranger vehicle. The soldier standing alongside Tillman described what he witnessed in a sworn statement.

"A GMV [vehicle] with a .50-cal rolled into our sight and started to unload on top of us," he said.

"Tillman and I were yelling 'Stop! Stop! Friendlies! Friendlies! Cease fire!' But they couldn't hear us."

According to another sworn statement obtained by CNN, the driver of the Humvee was initially confused when he saw the Afghan soldier with Tillman on the ridge -- and then realized others in his Humvee were firing on fellow Rangers.

"I yelled twice 'We have friendlies on top!'" said the driver. "The crew must have not heard me because my vehicle opened fired on them. I screamed, 'No!' and then yelled repeatedly several times to cease fire. No one heard me."

'We thought it was over'

Tillman threw a smoke grenade to signal they were Rangers, and for a few moments, it appeared to work.

Simply put, the family is not satisfied with the information they're getting. They've asked for more details, and simply put, we owe the family honest answers.

"We thought the battle was over," said the soldier next to Tillman. "So we were relieved, getting up stretching out and talking with one another when I heard some 5.56 rounds coming from the vehicle. They started firing again. That's when I hit the deck and started praying."

But Tillman didn't get down in time. He was hit.

"I know this because I could hear the pain in his voice as he called out: 'Cease fire! Friendlies! I am Pat (expletive) Tillman damn it!'" the soldier said. "He said this over and over again until he stopped."

Moments later, a sound caught the attention of the soldier next to Tillman.

"I heard what sounded like water pouring down," he said. "I then looked over at my side to see a river of blood coming down from where he was. I had blood all over my shoulder from him and when I looked at him, I saw his head was gone."

Fourth investigation launched

It has been two years since Pat Tillman was shot to death by his fellow Army Rangers in Afghanistan. There remain many unanswered questions about precisely how that happened.

In part because of the family's anger and disillusionment, the Pentagon has launched a fourth investigation -- a criminal probe into whether Tillman's death was negligent homicide -- as well as a separate review of whether the Army engaged in any intentional deception.

The other difficult thing, though, was watching some of these guys getting off, what I thought -- with what I thought was a lesser of a punishment than what they should've received.

"Simply put, the family is not satisfied with the information they're getting," said Col. Joseph G. Curtin, a U.S. Army spokesman. "They've asked for more details, and simply put, we owe the family honest answers."

The initial investigation -- conducted by an Army captain that CNN has identified as Richard Scott -- contains much harsher judgments than those reached in a later probe by a one-star general.

In a sworn deposition given five months after Tillman's death, Scott said that some stories "have changed. They have changed to, I think, help some individuals."

Scott said that in retelling, some distances have grown longer, some lighting conditions worse and even the position of the allied Afghan soldier was changed.

In his deposition, Scott said of one soldier in the lead vehicle that fired on Tillman: "I think [he] demonstrated gross negligence. ... He recognized the individual, the [Afghan] soldier wasn't shooting in his direction but shot and killed him anyway."

Scott noted that the Rangers in the lead vehicle firing on Tillman were not under fire at the time, and "there were numerous attempts to signal to that lead vehicle that the friendlies were upon that ridge line."

The documents show the numerous attempts to signal the lead vehicle included soldiers yelling into radios to cease fire, Tillman's smoke grenade, the driver of the vehicle yelling to cease fire, and finally Tillman and the soldier next to him waving their arms frantically over their heads.

But the firing continued, with no attempt to properly identify the targets, Scott asserted.

It was -- in Scott's opinion -- a lack of discipline that should have brought serious punishment.

"The other difficult thing, though, was watching some of these guys getting off, what I thought -- with what I thought was a lesser of a punishment than what they should've received," he said.

Uniform burned

The documents reviewed by CNN show the officer who made the original decision to split the platoon was later granted limited immunity to change his testimony about who above him knew about his order. He later explained that it was only a clarification of his original testimony.

The unit erred on the side of caution to get all the facts first to determine that indeed a friendly fire event had occurred. And that shouldn't have happened.

Tillman's uniform was burned by soldiers after his death. The Army's most recent investigation concludes Tillman's uniform and body armor should have been preserved, but the latest report disputes that it was burned in an attempt to cover anything up.

"Nothing could be further from the truth," concludes the report, which says the soldiers thought they were disposing of a "biohazard."

The Army said, so far, seven soldiers have received various reprimands.

"There were three officers and four enlisted personnel that were, all of them, were disciplined, all received administrative reprimands, one soldier was demoted and fined and three others were dismissed from the Ranger regiment itself," Curtin told CNN.

While no one was found "grossly negligent" nor "less than truthful" in the follow-up investigations --- more serious charges could result from the ongoing probe, which covers questions of criminal negligence, intent to cover up and the awarding of Tillman's Silver Star.

The Army said it learned a lesson from the delay in notifying the Tillman family about how their son died. The Army now has new procedures to ensure suspected friendly fire deaths are reported right away.

"The unit erred on the side of caution to get all the facts first to determine that indeed a friendly fire event had occurred," Curtin said. "And that shouldn't have happened. In hindsight, as soon as it was suspected they should have told the family about it."

The Army has expressed its deepest regrets to the Tillman family, and is promising the fullest accounting possible

"The bottom line is we will go where the truth leads us," said Curtin. We will get the answers to the best of our abilities."

For some of Pat Tillman's family that promise rings hollow. After two years of frustration, they wonder if a government investigation will ever uncover the truth.