Frank Gregg has been deployed to Afghanistan 12 times.

On his return home from his most recent tour, the U.S. Army staff sergeant and his wife, Dinah-Rhea Gregg, decided to surprise their two sons, Teagan, 6, and Tayden, 4.

The boys were staying at their maternal grandparents' Clarksville, Tenn., home for the night, and Gregg, 29, and his wife, 27, were on the way there. The boys got just minutes of notice from their grandmother.

"What would you say if we said daddy's coming in just a few minutes," their grandmother told Teagan on June 8.

Video posted on YouTube shows the boy's unexpectedly emotional reaction to news that he would see his father after the three-month absence.

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Teagan, who is shirtless, pauses to think for a few moments about what his grandmother said, and then he buries his face in his hands and bursts into tears.

Even when other family members give him construction paper and suggest that he make some signs for his father, he continues to sob.

Eventually he stops sobbing, wipes he eyes with his shorts, and says "My daddy's coming home." The gathered family members cheer and applaud, and Teagan gives a smile.

He runs to share the news with his younger brother, and then both boys wait outside their grandparents' home, both holding large U.S. flags. When their parents drive up and their father emerges from the car, his sons run to him and are swept up for tight hugs.

The boys' uncle Tommy Dabbs shot the video. He said he was touched by Teagan's initial tearful reaction to news of his father's imminent arrival.

"I kind of, I was behind the camera, I was kind of tearing up, of course, because we were expecting him just to be jumping up and down and kind of happy, and all of a sudden that emotion just came out and you know everybody there was kind of fighting back the tears a little bit," Dabbs told ABCNews.com in a Monday interview.

His sister, too, was taken aback when she saw her son's tears on the video.

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"I thought it was absolutely beautiful, the emotion that came out of him," Dinah-Rhea Gregg told ABCNews.com. "He's not a very emotional child anyway. I mean, he cries when he gets upset and stuff, but to see that reaction, it was just gut-wrenching. I mean, my husband, he says for him it shows how much he loves him, it meant how much he truly means to him and it was just so heartwarming."

She was also surprised by the number of views the video's had on YouTube.

"My brother did it just so I could send the video to my husband's parents, his family and then, of course, our family, which is obviously not 10,000 people," she said, referring to the number of views the video had had as of Monday afternoon.

She was struck by the idea of so many people watching her family, and said as much to her brother. He asked her whether she wanted the video to be put on a private setting. She didn't.

"I was like, I think it's important for people to see the effects of deployments on kids," she said.