Dan Caracciolo and Krissy Green were married Aug. 15 at Trump National Golf Club in Sterling. The two met on the course as coworkers in 2003. They became best friends and later fell in love. (Genevieve Leiper Photography)

In Aug. 2011, Krissy Green received the knock on the door that every military family fears and dreads; two uniformed soldiers had arrived to inform her that her younger brother, Spc. Douglas Green, had been killed in action in Afghanistan. He was 23 years old.

She immediately called her father to break the terrible news. The next call was to her best friend, Dan Caracciolo.

“That day completely changed my life forever,” says Krissy, a sales representative at Rockville-based Sage Software.

Dan and Krissy met on the golf course back in 2003, not as players, but as coworkers; the teens managed the beverage golf carts at what is now Trump National Golf Club in Sterling, Va.

Dan, then 18, had a love-at-first-sight moment when he saw Krissy on her first day of work. “The moment we locked eyes, time stood still,” Dan recalls. “I remember being taken back by how beautiful she was. She had this huge smile and these big, beautiful green eyes.”

Dan was too shy and afraid to ask Krissy for her telephone number. Luckily, Krissy, then 16, took matters into her own hands and nabbed his digits off the employee call sheet.

A friendship quickly developed, and the pair, who lived only five minutes apart, saw each other frequently. Although it was clear they had strong feelings for one another, they were scared to commit at such an early age.

Instead, they focused on strengthening their friendship rather than jumping into a relationship. “I think that was the best thing we could have done at the time,” Dan says. “It was a blessing that we didn’t, because I doubt if we did we would be here now.”

Things changed the day Krissy learned she had lost her brother. Dan, a middle school teacher, was coaching a soccer game when he realized he had three missed calls from Krissy, which was unusual. As soon as he got the chance, he broke away from the game and called her.

“She was screaming and crying. She kept repeating, ‘Dan, my brother died. Dan, my brother died,’ ” he says. “I just froze, and all the oxygen got sucked out of my lungs . . . and I raced to her as quick as I could.”

It was the catalyst that would bring them together as partners. Dan, who stayed by her side for weeks following her brother’s death, would prove to be her rock during the very difficult time.

“After all the people left . . . and the house was empty, that’s when it all started to hit home that everyone was gone. I felt alone,” Krissy says. “But Dan never left my side . . . That’s when I realized I wanted to marry him.”

He quickly ended a relationship with a woman he’d been seeing when he recognized his feelings for Krissy needed to be explored. “I reached a point where I felt I wanted to be by her side constantly,” he says.

A month after her brother’s passing, he took her out on their first date for her birthday; drinks at the Cheesecake Factory followed by dinner at Texas de Brazil in Fairfax City. It was a break they both desperately needed and a chance to have a moment alone together to reflect.

A few weeks later, they traveled together to Las Vegas to spend Thanksgiving with Krissy’s mother and stepsister, which further validated their connection.

“It felt like every day our feelings were growing for one another. She was opening up more to me, and I knew that was tough for her, especially since she was dealing with the loss,” Dan says. “That’s when we discovered we were in love with each other. . . . We were each other’s yin and yang. And I realized then this is what I want for life.”

Soon after her brother’s passing, Krissy started the Douglas J. Green Memorial Foundation, a nonprofit organization that collects money to send care packages to military service members overseas. “It was my coping mechanism,” she says.

Dan helped her get the foundation off the ground and today devotes his free time to helping her coordinate and organize fundraising events. “He definitely is my right-hand man,” she says. “And for me, that speaks volumes that he appreciates and supports everything I want to do in life.”

On Christmas Eve in 2013, the pair exchanged gifts at their apartment. Unwrapping her last present, Krissy unveiled a crystal glass ornament, which read, “Our First Christmas — 2013,” with an engagement ring tied to its ribbon. By the time she realized what was happening, Dan had dropped to one knee.

Krissy Green, 27, wed Dan Caracciolo, 29, on Aug. 15 at the place where they first met, Trump National Golf Club. The couple made sure Douglas was very much a part of their wedding; he was Dan’s honorary groomsman, his dog tags graced Krissy’s bouquet and a third chair was added to their sweetheart table, containing his flag, his picture and his favorite drink. More than 200 guests waved individual American flags as the couple made their exit.

After the wedding, Krissy and Dan spent a six-day honeymoon in the Riviera Maya in Mexico. “A lot of people have recommended all these different excursions, boating to kayaking, this or that, but honestly we will just be glad to put our butt in the sand and get a drink in our hand,” Dan says. “It’ll be tough to deviate from that plan.”