The story behind the stunning photo of a bride gasping in surprise as she walks down the aisle has captured the hearts of tens of thousands of people.

An Alaskan wedding photographer posted to Facebook a series of photos surrounding the touching moment last weekend, garnering hundreds of thousands of likes, shares and comments in days.

The bride, Becky Turney, had a 19-year-old son, Triston, who died in October 2015 in an accidental shooting, according to Turney's Facebook page. His heart was donated to a young California man named Jacob Kilby, whom Beckey had never met.

Becky's groom, Kelly Turney, surprised her at their wedding by flying Jacob up to Alaska to stand in as a groomsman. Kelly stopped the ceremony to introduce Jacob to Becky for the first time, the photographer recounted.

"I knew about this surprise but nothing prepares you for the beauty of this moment," the photographer wrote on the Love Adventured Facebook page.

The photos show Becky gasping, then hugging the 21-year-old Jacob in tears. Another photo shows her smiling as she holds a stethoscope to his chest, then holding her hand to her mouth as she listens to his heart beating.

Becky's bridal bouquet also had tiny framed photos of Triston wrapped around it.

The wedding photographer said she was "blown away" by Jacob's story and his "amazing outlook on life."

"You couldn't ask for a better recipient to receive such a gift," the photographer wrote.

Becky wrote in a subsequent Facebook post of her own, "Jacob, hands down the best gift, most amazing surprise ever!! Thank you for caring for Triston's heart. Thank you for being here! Thank you thank you thank you!!"

Becky had shared the news of her teenage son's death in a public Facebook post dated Oct. 18, 2015. She wrote that the event "was a tragedy and senseless."

"Triston is an organ donor and will be able to help someone's life or allow someone the gift of sight or both," she wrote. "He's one amazing man and I'm quite proud of him."

The recipient of Triston's heart was Jacob, a surfer from San Diego, who was born with a rare condition where the left side of his heart didn't fully develop, according to a 2014 post written by his aunt on the Pediatric Congenital Heart Association page. He had four open heart surgeries, all of which failed, and finally, before he was 3 years old, got a heart transplant that "saved him just in the nick of time."

He sailed through school, was liked by everyone and "adored and treasured" by his family; "his smile shines so bright," his aunt wrote.

But by the time he was 19, he needed a new heart. And, she wrote, he was at a "stage two" on the waitlist, where "he really has no chance of getting a new heart."

"Those who receive organs are those who are on the list the longest and those who are the sickest," she wrote. "So I guess things haven't changed in that respect in the 17 years that he'd had his donor heart... Here we are again."

Around that time, Make-A-Wish flew Jacob out to Hawaii to meet and surf with local surfing pros Jamie O'Brien and Bruce Irons, according to TheSurfChannel.com. By then, his doctors had advised him to not attend college and to quit his job.

In the end, though, Jacob got a new heart.

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