A couple shared how they were given a secret act of kindness after encountering a celebrity while out shopping.

In 2004, Kyle and Kristen Upham had gotten engaged and were visiting a jewellery store in Santa Barbara to shop for a ring.

As the couple browsed the store, another shopper began to help them with their purchase.

Kyle had been due to be deployed to Iraq for a second tour of duty, and the pair wanted something special before he left.

The stranger had looked at rings along with them, with neither of them realising who he was.

Speaking to CBS in 2013, Kyle said: “I noticed there was someone else in there, but didn’t give it much thought, and we started looking at rings and whatnot, and he kept saying, ‘Go bigger’ and I kept saying, ‘No, look at the prices.’”

Kyle and Kristen left the shop without making a purchase, but despite their initial disappointment, they had a wonderful surprise.

While they didn’t realise at the time, the couple later found out that the mystery shopper had been none other than Paul Walker, star of the Fast and Furious movies.

The couple had been shopping for an engagement ring (Facebook)

“When we were talking, we exchanged names and talked about what each of us did,” said Kyle, with Kristen adding: “And when he found out Kyle just came back from Iraq — I remember seeing the look in his face, he kind of transformed.”

After they left, they got a call from a salesperson at the store who told them to come back.

Kristen recalled what happened next, saying: “One of the ladies came out holding a bag and just said, ‘Here’s your ring.’ I think both of our mouths dropped.”

She added: “It’s still to this day the most generous thing anyone has ever done for me.”

The couple initially thought that the store staff might have banded together to get them the ring, before they remembered the mystery shopper Paul Walker.

Their suspicions were confirmed when a clerk at the store revealed what had happened to CBS.

They later found out that Paul Walker had bought them the ring (Steve Granitz/WireImage)

Irene King had been on shift that day, and recalled how a colleague had told her that Paul Walker was in the shop at the same time that Kyle and Kristen were browsing rings.

“She saw something that she really, really liked, but he said, ‘Honey, I can’t afford that,’” King told CBS in 2013.

She added: “He [Walker] called the manager and he said, ‘Umm, the ring that those people are looking at – put it on my tab.’ Soon after that, he just left.”

The store told Kyle and Kristen it had been an anonymous gift, and kept the secret for ten years.

Kyle and Kristen and King shared the story after Walker’s death in a car crash in 2013.

“When we hand down the ring through the generations, there will always be a story to tell,” Kyle said.

“His real life speaks volumes of his character,” Kristen added. “He really did put his money where his mouth is and did good for this world.”