(CNN) Humayun Khan knew he was walking toward danger. He must have known.

The 27-year-old Army captain had ordered those around him to take cover as soon as he saw a taxi barrel through the gates of his base in Baquba, Iraq. He took 10 steps toward it before it exploded.

Khan isn't the only Muslim-American to give his life in the service of his country. But in this rancorous political climate, where Republican presidential nominee Donald Trump is calling for a ban on Muslims, his story has taken on a different sort of significance.

And when Khan's parents strode on to the stage at the Democratic National Convention, their grief still writ large on their faces 12 years later, it was a meeting of identities as potent as the symbol on the Army captain's military grave.

It signaled that patriotism and Islam are not mutually exclusive, that sacrifice and grief have no religion, and that the similarities the Khans share with so many American families are far more meaningful than their differences.

American opportunities

Humayun Khan was born in the United Arab Emirates to Pakistani parents. His family moved to America 36 years ago.

"Like many immigrants, we came to this country empty-handed. We believed in American democracy; that with hard work and goodness of this country, we could share in and contribute to its blessings," the father, Khizr Khan, said during his speech Thursday night at the Democratic convention.

"We are blessed to raise our three sons in a nation where they were free to be themselves and follow their dreams."

The family settled in Maryland, where the boys seemed to have a knack for academics.

Khan enrolled in the ROTC program at the University of Virginia after completing high school. He graduated with a degree in psychology.

He aspired to be a military lawyer, and wanted a career advocating for veterans. He decided to join the Army first to pay for law school.

American sacrifice

On the day he died, Khan was overseeing soldiers as they conducted routine vehicle inspections. It was June 8, 2004 -- the height of the insurgency when attacks on American forces were constant.

He'd last talked to his mother a month earlier, on Mother's Day.

"Whenever I talked to him, I started to cry," his mother, Ghazala, told The Washington Post at the time . "He always said to me, 'Don't worry. I'm safe.' "

Laci Walker, who was a sergeant under Khan, described him as a first-rate and admirable leader, and the man she most respected other than her father and husband.

The country should honor Khan for character, not his ethnicity, she said.

"He didn't wear his heritage on his shoulder; he wore the American flag like we all did," she said. "He was definitely the best leader, and I was devastated by his loss, and I have a tattoo in his honor.

Khan was an ordnance officer with the 201st Forward Support Battalion, 1st Infantry Division. His unit made sure the camp stayed secure and things ran smoothly.

While serving, he also participated in a U.S. Army program that helped Iraqi citizens earn money to support themselves.

"He was always a peacemaker," his father told the Post . "[He was] always seeing an opportunity to give. He was always to the Iraqis, 'We're here not to hurt you but to help you.'"

When the taxi drove through the gates, Khan told the soldiers to take cover. He walked toward it, signaling for it to stop.

The car, with 200 pounds of explosives, blew up, killing him.

Khan's actions saved the lives of several others. For that, he was awarded a Bronze Star and a Purple Heart.

"He died selflessly and courageously, tackling the enemy head on," his commanding officer, Lt. Col. Dan Mitchell, wrote in a letter read at his funeral. "We will not forget him and the noble ideas he stood for."

He was given full military honors and buried at Arlington National Cemetery, where the marble headstone bears the star and crescent of his faith He was 27.

Visitors pay tribute at grave

Cards and flowers have been laid on Khan's grave in section 60 of the cemetery by visitors paying their respects.

Quiet, steady stream of visitors at @ArlingtonCem today to honor #HumayunKhan. Took my turn, with other families. pic.twitter.com/hMBuZ4eQeg — Holly Shannon (@7OYShannonABC7) August 1, 2016

Brian Butler came by on Sunday, according to CNN Affiliate WJLA

"They had so many people come up and see his grave, different races, it was just a stream of people," Butler said. "Just feeling for his parents and feeling a loss, no matter what party you're affiliated with."

American perspective

At least 6,024 Muslims have served in the U.S. armed forces since the September 11 terror attacks, and at least 14 have died. Those figures are from a Committee on Homeland Security report issued in 2011.

But those numbers are only for service members who self-identified as Muslims. The Pentagon does not track recruits by faith. They only ask service members to declare their faith on their records so that in case of death, the department can provide the correct religious chaplain.

American family

The convention stage was an unexpected destination for Khan's parents, one they could not have foreseen.

Khizr Khan spoke briefly of his son, but focused most of his words on what it meant to be an American Muslim and the discontent he felt with Donald Trump's plans for people like him.

At one point, he reached into his breast pocket and pulled out a small copy of the U.S. Constitution. A Muslim immigrant, holding aloft one of the country's most important documents and urging his fellow citizens, and his leaders, to consider its words.

"In this document, look for the words 'liberty' and 'equal protection of law,'" he said. Specifically addressing Trump, he asked, "Have you ever been to Arlington Cemetery? Go look at the graves of brave patriots who died defending the United States of America."

"You have sacrificed nothing and no one."

#dnc #khizrkhan #fuckyoutrump #imvotingforhillary A photo posted by Julie Wilson (@juliewilsonillustration) on Jul 29, 2016 at 12:26am PDT

His gesture set off a seismic reaction. Supporters typed out Khan's words and superimposed them over images of him holding up that little blue book. Some shared pictures of their own copies of the Constitution.

#khizrkhan loves his pocket constitution as much as me! Mine is pictured below, well worn, and well loved. #USA pic.twitter.com/3SsedMGezJ — Sarah Dew (@CapaDew7) July 29, 2016

The elder Khan is a Harvard-educated lawyer who now lives in Charlottesville, Virginia, and works as a legal consultant. Journalist Wajat Ali reported the worn Constitution that Khizr Khan produced, a totem of true American-ness, was far from a prop.

He's carried it with him for years.