An emotional video gone viral shows a South Dakota boy present his unsuspecting grandfather with an autographed game ball after hitting his very first home run.

Melissa Carrier-Damon, who posted the video, said her 9-year-old son Felix has been playing baseball since he was 4 years old, and this year, began playing for a traveling baseball team in Sioux Falls.

Carrier-Damon, 38, told USA TODAY that during a recent game Felix hit his first home run – and then a grand slam.

That afternoon, she said, her son decided to thank his grandfather for teaching him how to play ball. Without her dad’s knowledge, Carrier-Damon secretly filmed it.

“I had no idea what that little video would do,” Felix’s mom, 38 said.

In the the 36-second video, the boy approaches his grandfather, Bruce Carrier, who he calls “Papa”.

“So you know I got two home runs, right?” Felix said to Carrier as the duo stand inside a garage. “I signed the ball for you and it says ‘Papa I love you’.”

“Why did you do that?” Carrier asked, starting to become emotional.

“Because you taught me everything about baseball,” the boy replied, then bear hugged his grandfather who appeared to cry.

“Wow, honey, whoo!” Carrier eventually replied.

Carrier, a retired school superintendent in South Dakota and grandfather of nine, told USA TODAY he was overjoyed about his grandson’s gift.

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“He shot it down left field … and it started rolling down to the fence and he kept running, running, running,” said Carrier, a former college basketball coach at the University of Missouri, Kansas City, and at Huron College in South Dakota. “You get two home runs inside the park as a third grader, to me that’s exciting. I was so happy for him.”

“I got emotional. I’m not ashamed of it at all,” Carrier said. ” He gave me something to be part of his day. To share that day with him. … That was awesome.”

Carrier said he was unaware his daughter filmed the treasured memory until the video started popping up online – it’s gotten nearly 500,000 views on Instagram.

“The look at the end of his face looking up at me,” Felix’s grandfather said as he recalled watching the video. “I still get teary-eyed looking at that. I’m so proud he let me be part of that day.”