Image copyright Mark Brunner

In 1996, a black teenager protected a white man from an angry mob who thought he supported the racist Ku Klux Klan. It was an act of extraordinary courage and kindness - and is still inspiring people today.

Keshia Thomas was 18 when the Ku Klux Klan, the white supremacist organisation, held a rally in her home town in Michigan.

Liberal, progressive and multicultural, Ann Arbor was an unusual place for the KKK to choose, and hundreds of people gathered to show them they were not welcome.

The atmosphere was tense, but controlled. Police dressed in riot gear and armed with tear gas protected a small group of Klansmen in white robes and conical hoods. Thomas was with a group of anti-KKK demonstrators on the other side of a specially-erected fence.

Then a woman with a megaphone shouted, "There's a Klansman in the crowd."

They turned around to see a white, middle-aged man wearing a Confederate flag T-shirt. He tried to walk away from them, but the protesters, including Thomas, followed, "just to chase him out".

Image copyright Mark Brunner

It was unclear whether the man was a Ku Klux Klan supporter, but to the anti-KKK protesters, his clothes and tattoos represented exactly what they had come to resist. The Confederate flag he wore was for them a symbol of hatred and racism, while the SS tattoo on his arm pointed to a belief in white supremacy, or worse.

'I am kinder thanks to her' Image copyright Other Teri Gunderson, who now lives in Oaxaca, Mexico, emailed BBC News Magazine about her respect for Keshia Thomas when we published a series about kindness earlier this month: "Her courage so touched me that I keep a copy of the picture and often think of her in situations. "The voice in my head says something like this, 'If she could protect a man [like that], I can show kindness to this person.' And with that encouragement, I do act with more kindness. I don't know her, but since then I am more kind." Can we teach kindness? Special report: Making Time

There were shouts of "Kill the Nazi" and the man began to run - but he was knocked to the ground. A group surrounded him, kicking him and hitting him with the wooden sticks of their placards.

Mob mentality had taken over. "It became barbaric," says Thomas.

"When people are in a crowd they are more likely to do things they would never do as an individual. Someone had to step out of the pack and say, 'This isn't right.'"

So the teenager, then still at high school, threw herself on top of a man she did not know and shielded him from the blows.

"When they dropped him to the ground, it felt like two angels had lifted my body up and laid me down."

For Mark Brunner, a student photographer who witnessed the episode, it was who she saved that made Thomas' actions so remarkable.

"She put herself at physical risk to protect someone who, in my opinion, would not have done the same for her," he says. "Who does that in this world?"

Image copyright Mark Brunner Image copyright Mark Brunner Image copyright Mark Brunner Image copyright Mark Brunner previous slide next slide

So what gave Thomas the impetus to help a man whose views it appeared were so different from her own? Her religious beliefs played a part. But her own experience of violence was a factor, too.

More from the Magazine Image copyright Getty Images The Confederate flag wasn't a major symbol until the Civil Rights movement began to take shape in the 1950s, says Bill Ferris, from the Center for the Study of Southern Culture at the University of Mississippi. It had been relegated to history, but the Ku Klux Klan and others who resisted desegregation turned to the flag as a symbol, he says. Read more: Why do people still fly the Confederate flag?

"I knew what it was like to be hurt," she says. "The many times that that happened, I wish someone would have stood up for me."

The circumstances - which she does not want to describe - were different. "But violence is violence - nobody deserves to be hurt, especially not for an idea."

Thomas has never heard from the man she saved, but she did once meet a member of his family. Months later, someone came up to her in a coffee shop and said thanks. "What for?" she asked. "That was my dad," the young man replied.

For Thomas, the fact that the man had a son gave her actions even greater significance - she had potentially prevented further violence.

"For the most part, people who hurt... they come from hurt. It is a cycle. Let's say they had killed him or hurt him really bad. How does the son feel? Does he carry on the violence?"

Image copyright Mark Brunner Image caption Keshia Thomas (left) pictured before the rally with friends

Teri Gunderson, who was bringing up her two adopted mixed-race daughters in Iowa at the time, was so touched by Thomas' story that she kept a copy of her picture - and still looks at it 17 years later. Gunderson even thinks the student made her a better person.

"The voice in my head says something like this, 'If she could protect a man [like that], I can show kindness to this person.' And with that encouragement, I do act with more kindness. I don't know her, but since then I am more kind."

'Keshia's choice was hope' "That some in Ann Arbor have been heard grumbling that she should have left the man to his fate, only speaks of how far they have drifted from their own humanity. And of the crying need to get it back. Keshia's choice was to affirm what they have lost. Keshia's choice was human. Keshia's choice was hope." By Pulitzer Prize-winning commentator Leonard Pitts Jr. The Miami Herald, 29 June 1996

But she asks herself whether she could be as brave as Thomas. What if one of the hurtful people who had racially abused her girls was in danger, she wonders. "Would I save them, or would I stand there and say, 'You deserved it, you were a jerk.' I just don't know the answer to that, yet. Maybe that is why I am so struck by her."

Brunner and Gunderson both often think of the teenager's actions. But Thomas, now in her 30s and living in Houston, Texas, does not. She prefers to concentrate on what more she can do in future, rather than what she has achieved in the past.

"I don't want to think that this is the best I could ever be. In life you are always striving to do better."

Thomas says she tries to do something to break down racial stereotypes every day. No grand gestures - she thinks that small, regular acts of kindness are more important.

"The biggest thing you can do is just be kind to another human being. It can come down to eye contact, or a smile. It doesn't have to be a huge monumental act."

Looking back at his photos of Thomas pushing back the mob that day in June 1996, Brunner says: "We would all like to be a bit like Keshia, wouldn't we? She didn't think about herself. She just did the right thing."

Follow @BBCNewsMagazine on Twitter and on Facebook