Man Dies One Day After Paying Stranger's Grocery Bill, Inspires 'Pay it Forward' Movement Matthew Jackson was killed in a car crash one day after his act of kindness.

 -- A California man's legacy is spreading across the world after showing a stranger a random act of kindness just one day before losing his life in car accident.

"How does somebody do something so kind and so generous and then have something so tragic happen to them the very next day?" Jamie-Lynne Knighten of Carlsbad, California told ABC News. "The fact that he was gone and I couldn't give him a hug or say 'Thank you,' it broke my heart. It was just very surreal."

"I cant imagine what his family is going through, given that I only knew him for five minutes."

Knighten said it was on Nov. 10 when she and her son Wyatt, 5 months, ran into some trouble when they left their debit card at home as they were about to pay their grocery bill at a Trader Joe's market in Oceanside, California.

That's when, she said, a stranger named Matthew Jackson, 28, approached her with an extremely sweet offer.

"Matthew steps up to me and said 'May I?' and I said 'May you what?'" Knighten recalled. "He said 'May I take care of your groceries?' I told him 'No,' and that it was a very large purchase. He really wanted too. He said, 'You just have to promise that you'll do it for somebody else.'"

Knighten said Matthew paid for her $200 grocery bill after she promised him she'd pay the kindness forward.

One week later, Knighten said she called LA Fitness in Oceanside, where Matthew told her he was working, in order to thank him for his generosity. But the health club's operations manager told her that Matthew had passed away on Nov. 11 in a car crash--just one day following his act of kindness at the grocery store.

Saddened by the news, Knighten asked Matthew's co-workers to connect her with his mother so she could share the news of what he did for her.

"I knew he had a kind heart towards people, but hearing all these stories goes beyond what I knew," Matthew's mom LeeAnn Krymow told ABC News. "What was very odd to me was that it [the act of kindness] happened on my birthday and when he got home that night he must have called me right after he got home from Trader Joe's, wishing me a 'Happy Birthday.' It was late and I was already in bed, so I didn't take the call. I still regret not taking the call.

"[The next day] I sent him a picture, blowing him a kiss and that was it," she added. "I never heard back. Matthew was always special to me. He was really intelligent, good looking...he was every girl's prince charming. He was known for being a gentleman. He loved people. He had a heart for people and so much compassion."

In an effort to create a vessel for paying it forward, Krymow said Knighten approached her with the idea for "Matthew's Legacy"--a platform where strangers could read Matthew's story and share their own random acts of kindness in his honor.

The pages on Twitter and Facebook have since generated tales of kind acts from all over the world.

Krymow said she hopes her son's legacy inspires people to keep kindness a part of their everyday lives, just as Matthew would've wanted.