A Once in a Lifetime Kid - The Pat Tillman Story. Listen to BBC Radio 5 live from 2030 BST on Thursday.

In these days when money often seems to be the main motivating force in professional sport and loyalty is in short supply, it's rare to come across a story like that of Pat Tillman. But then Pat Tillman was no ordinary sports star.

This is a man who turned his back on a multi-million dollar contract in one of the richest sports in the world to serve his country - and paid the ultimate price.

I travelled to Tillman's home city, San Jose in Southern California, to meet members of his family, friends and close colleagues, and came away with one regret - that I never had the chance to meet the man himself.

Pat Tillman bears down on an opponent during his NFL career. Photo: Getty

Ten years ago, Pat Tillman was playing safety for the Arizona Cardinals in the NFL - not the tallest, at 5ft 11in, but one of the most dynamic defensive players in the league. Watch video footage of him in action and you'll see him flying into tackles with no sense of fear, or charging downfield with his mane of blond hair flopping underneath his helmet.

He was a star of his college football team at Arizona State University when Frank Bauer, who would become his agent, first met him.

Bauer told me he'd never met anyone quite like Pat. "Here's this kid in shorts and flip flops, with long blond hair - the kind of person you think will become a doctor rather than a football player," said Bauer. "When I met him, he showed up on a bicycle. Most players show up in a brand new car, thinking they're going to make it in the NFL. But not Pat."

It was touch and go whether Tillman made it as a pro footballer at all - he was one of the last players to be picked in the 1998 NFL draft, by the Cardinals, and he remained loyal to them throughout his career, at one point turning down a contract from the St Louis Rams which would have nearly quadrupled his annual salary.

But the life of Pat Tillman and his family changed for ever on 11 September 2001. Watching the shocking pictures from New York and Washington, Tillman was deeply affected. A day later, he gave a TV interview:

"My great-grandfather was at Pearl Harbour and a lot of my family have gone and fought in wars. I really haven't done a damn thing as far as laying myself on the line is concerned. So I have a great deal of respect for those who have and for what the flag stands for."

It was to be the last interview he would ever give.

At the end of the 2001 season, Tillman turned down a hugely improved contract from the Cardinals. The following June, a month after marrying his high school sweetheart Marie, he and his brother Kevin enlisted in the US Army.

Typically of Tillman, he didn't go for the easy option. He joined the elite Army Rangers. As a number of people told me, they wouldn't have been surprised to hear that Tillman had single-handedly tracked down and captured Osama Bin Laden himself.

And Pat certainly wasn't doing it as an ego trip. Numerous requests for media appearances were turned down by his agent.

"We had everybody contact us - Oprah, Larry King, Good Morning America - wanting Pat to be on the show," Bauer says. "He would call back and say - 'Frank, you need to handle this. There are thousands of men and women in armed service - what makes me so special?' Then I had a call from the Pentagon. They said, this is a great thing that Pat Tillman has done. We want to keep him out of harm's way. We'd like to have him travel throughout Europe and the Middle East and encourage our armed forces. Pat said, 'I'm not doing that, I don't want to prostitute myself!'"

There was no question of Pat Tillman being turned into a poster boy for the Pentagon, and he was reportedly unhappy to be sent to Iraq in 2003 - this wasn't the war he had signed up for. When he returned from Iraq, he was given the chance to leave his army contract early, having served in a war zone. But again Tillman turned his back on the prosperity and comfort of a football career, and in 2004 he was finally deployed to Afghanistan.

On 22 April 2004, his family received the news they'd dreaded. At the age of 27, Pat Tillman was dead.

Pat's platoon had been travelling through the mountainous Khost province, near the border with Pakistan. Following orders from above, the unit was split into two, with Pat in the forward party and his brother Kevin in the second group, a few minutes behind. As the second group moved through a canyon, they were ambushed from above. Pat and two other soldiers left their vehicles and doubled back onto the hillside to defend their comrades, but as the besieged convoy emerged into daylight, Pat and his men came under heavy fire, and he was shot three times in the head.

In the days which followed, the Army rushed to grant posthumous decorations. The citation which accompanied the Silver Star approved by Lt Gen Stanley McChrystal included the phrase "in the line of devastating enemy fire".

Back in San Jose, a memorial service was held in the Municipal Rose Garden, attended by luminaries from the NFL and with speakers including future presidential candidate Senator John McCain and the then wife of California Governor Arnold Schwarzenegger, Maria Shriver.

There was a stark contrast between the words of those who knew Pat personally and of those who didn't. Before he spoke, his brother-in-law and close friend Alex Garwood poured a pint of Guinness and placed it on the lectern. Younger brother Richard thanked those who'd spoken but said: "Pat would want me to say this, he's not with God, he's dead. He's not religious."

Less than a month later came the news that would devastate his family for a second time. The bullets that had killed Pat Tillman came not from a Taliban fighter, but, in the panic and confusion of the ambush, from one of his own men.

Gradually, as Mary pushed for the truth of what had happened to her son, more details emerged. It became clear that Tillman's death had become the subject of a major cover up. She discovered that the autopsy following his death hadn't been properly carried out, and that his body armour and his diary had been burnt before his body was repatriated, all against Army protocol.

In 2008, a House Committee on Oversight and Government Reform report stated that its "investigation was frustrated by near universal lack of recall" among "senior officials at the White House" and the military. "It is clear that the Defense Department did not meet its most basic obligations in sharing accurate information with the families and with the American public".

That same year, Mary Tillman wrote a book about the devastating experience of hearing of her son's death, and she's been reluctant to be interviewed since then. It's not hard to imagine the pain she went through at that time. But she did agree to talk to us about his life and her attempts to find out the truth about how he died.

She said: "The hardest part is knowing he was trying to do the right thing, and that he was used...that was really hurtful. I hurt for him. And even the fact that he was turned into some kind of icon. Pat had so many good qualities, but he was a human being, and that was stripped from him."

The Pat Tillman Foundation was set up shortly after his death by his family, providing support and education for veterans and active servicemen and women. But his lasting legacy comes from the memories of those who knew and loved him best, including brother-in-law Alex Garwood, who said: "I love his thirst and desire to learn, to improve himself, to ask questions. The world was a better place with him in it - but particularly with him in it in your presence. He is one of the best people I've ever met. And he still is."