A crowd cheered as three border agents propped open a heavy metal gate known as the “Door of Hope” — a rare, fleeting opening in the 2,000 mile border between the United States and Mexico.

Twelve families lined up on Saturday at the door straddling San Diego and Tijuana, Mexico, for their chance to see their loved ones on the other side — for all of three minutes each. For the sixth time in recent years, the Border Patrol agreed to open the door, according to Enrique Morones, executive director of the Border Angels group that organizes the events.

Much like other years, relatives shed tears as they embraced. A woman introduced her three children to their grandparents in Mexico for the first time, while a the man reunited with his mother for the first time in 12 years.

But then, in the last of the 12 reunions, an unexpected gathering took place: a wedding.

The bride, Evelia Reyes, 27, appeared on the Mexico side in a long white wedding dress, complete with a flowing train and veil. On the U.S. side was her groom, Brian Houston, 26, donning a light gray suit.

Reyes’s young daughter, also wearing a white dress and tiara, jumped into Houston’s arms just before the groom kissed his bride, holding them both close for a long moment.

Standing beside a judge from Tijuana, and inches away from hovering border agents, the couple signed documents and exchanged their vows. They each brought their own wedding ring, since they could not move any items across the border.

And then, after three minutes, Morones had to tell the newly wedded couple their time was up.

“I am happy and sad at the same time,” Reyes told AFP, “because now I have to leave.”

The gate opened in Friendship Park, the only federally designated binational meeting place along the border between the U.S. and Mexico. Each Saturday and Sunday, the park opens from 10 a.m. to 2 p.m., allowing families to see each other through a steel mesh fence. The holes in the fence are just large enough to let through a fingertip.

Border Angels began coordinating the gate openings since 2013, when Border Patrol agreed to open the doors for two minutes in celebration of Children’s Day in Mexico. Agents have allowed the door to be opened five more times in the years since, including twice this year.

Each of the 12 families were selected by Border Angels for reunion on a first-come-first serve basis. Each person applied for the visit about two months ago, and was subject to background checks by federal authorities before approval.

Morones, who was in charge of the event, said Houston told him he wanted to ask Reyes to marry him.

“I thought it was just a proposal,” he said. Morones was not expecting the bride to show up in a full wedding gown, with a judge and witnesses close behind.

“It was unbelievable,” Morones said. “It was such a mixture of emotions.”

Talking by phone before the planned opening, the couple decided they could not wait any longer to get married. They would do it right then, during their three-minute embrace.

After the gate had closed, Houston and Reyes shared a private moment together, speaking through the steel mesh fence until the park closed at 2 p.m., Morones said.

“I spent a long time waiting for this,” Reyes told AFP. “I believe that hope is the last thing that dies, and this is proof that things are possible.”

“The wall doesn’t really exist,” she said. “It is there physically, but that’s it.”

Reyes, a native of the southern Mexican state of Guerrero, met Houston in Tijuana three years ago. She has two children from a previous marriage — both of whom accompanied her on Saturday.

They talk by phone every day, and see each other through the fence on Saturdays and Sundays, Morones said.

The couple is working with an immigration attorney to get Reyes a green card to come to the U.S., which could take more than a year, the San Diego Union-Tribune reported.

“Hopefully very soon she can get a visa to come here and we can be together again,” Houston told Reuters.

Houston is a U.S. citizen who was born in San Diego but cannot currently leave the country. He did not elaborate on why. But after a screening by federal officials, he was granted permission to see Reyes on Saturday.

Saturday’s scene in stark contrast to when the park was first inaugurated, in the summer of 1971. Then-first lady Pat Nixon walked up to what was then a barbed wire fence, and asked her security escort to cut an opening. She stepped easily into Tijuana.

“May there never be a wall between these two great nations,” the first lady said. “Only friendship.”

Now, decades later, Saturday’s event took place just 15 miles west of the site of prototypes for President Trump’s promised border wall.

The prototypes, 30-foot tall concrete and steel sample barriers, some topped with metal spikes, are an ominous reminder of what the border could soon become.

But those prototypes — and Trump’s future wall — felt far away on Saturday for those families enjoying the brief but lasting moments with their loved ones.

“It’s a wonderful thing, after 12 years, to be able to hug my son, to meet my grandchildren, to have them close,” a Mexican national, Carmen Sanchez told AFP. “It was something wonderful . . . it’s something I can’t describe because it was such a great joy.”

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