Moments after 94-year-old Harriette Thompson crossed the finish line at at the 2017 Synchrony Financial Rock ‘n’ Roll San Diego Half Marathon, purple confetti blasted into the air.

The color selection for the paper celebration proved fitting. Purple is the hue of choice for the Leukemia & Lymphoma Society’s Team-In-Training program, and wanting to fight cancer is the reason Thompson took up long-distance running at the sprite age of 76.

“I’ve lost everyone in my family to cancer,” said Thompson, who lives in Charlotte, N.C., and has raised more than $100,000 for LLS. “Leukemia & Lymphoma means a lot to me.”

At the corner of Ash and State streets in downtown San Diego on Sunday, Thompson set history for the second time, becoming the oldest woman to run a half marathon. Her feat came two years after Thompson, then 92, became the oldest woman to finish a marathon, again at Rock ‘n’ Roll San Diego.

Come Monday morning, in the comfort of her hotel room that overlooked yachts on San Diego Bay, one of the first things Thompson did was pray.

“I was trying to figure out what I would do for the rest of my life,” said Thompson, barely five years shy of 100. “How I could be a good influence on people and make the right choices? It’s very difficult to express what I was feeling. I was praying that I’d make the right choices, praying I could make other people feel good.”

Then she thought of the simplest thing anyone can do to brighten someone’s day.

“I find that if you smile it does something to your brain,” she said. “You can’t have an evil thought when you’re smiling. I think it makes others feel good. I want to keep smiling, making life pleasant for other people.”

There is irony in Thompson feeling so passionate about wanting to influence others in her final years because it’s something she’s already accomplishing.

“You’re my inspiration!” runners and walkers serenaded to Thompson along her 13.1-mile trek Sunday.

Thompson, who has battled three bouts of cancer, was joined in San Diego for the half marathon by two of her sons, granddaughter Angela Thompson, and one of her son’s girlfriend. The foursome formed a sort of cocoon for Thompson, running on both sides and behind her lest an overzealous fan get too close and knock her off balance. Thompson has battled vertigo the past year.

Said her son, Sydnor, “I realized my mother had gained a certain amount of fame when everyone refers to her simply by her first name.”

In the post race VIP area, as the band “Michael Franti and Spearhead” rocked spectators, Thompson’s breakfast burrito nibblings were interrupted often by spectators wanting to pose for selfies with Thompson.

Among those posing with Thompson: Boston and New York City marathon champion Meb Keflezighi, who paced 90-minute half marathon finishers.

Well aware that Thompson is a concert pianist with performances at Carnegie Hall, Keflezighi said, “She has proven what music and exercise does for the body and soul.”

Later, Thompson stepped on stage with the band, greeted by spectators chanting, “Harriette! Harriette! Harriette!”

Thompson’s story has been told often, particularly in Charlotte and San Diego, where she is the out-of-towner locals never tire of hosting. She was 75 years old, singing in the church choir when she noticed another singer collecting checks.

The woman explained she would be walking a marathon in San Diego and was raising money for the Leukemia & Lymphoma Society.

“I can walk a marathon,” said Thompson.

A year later, at 76, Thompson jogged her first marathon.

“Harriette has inspired so many people to join the Leukemia & Lymphoma Society, to sign up for their first marathon or half marathon,” said Abby Miller, a regional Team-In-Training director. “To make people realize age does not mean anything.”

Asked what she has learned about herself, Thompson said, “I’ve been interested in wondering why I seem to have more energy and strength and endurance to do this.

“I think it’s probably because I had four brothers who toughened me up when I was little. (They would sometimes flick her ears when she practiced at the piano.) They really gave me a hard time. I learned to cope with their teasing me.”

As for her much longer than 15 minutes of fame, Thompson said, “I didn’t plan on breaking any records. I was just always interested in getting a little funding for the Leukemia & Lymphoma Society.”