(Credit: Mike Tapscott / American Military Partner Association)

U.S. Marine Corps Capt. Matthew Phelps made history Saturday at the home of his commander in chief.

The 35-year-old active-duty officer proposed to his boyfriend, Ben Schock, 26, in the Grand Foyer of the White House at the end of a holiday tour.

It's believed to be the first time two gay men have gotten engaged inside the White House, and a first for an active-duty member of the U.S. military. A transgender man proposed to his partner in the East Room earlier this year.

"Our first date was to the White House, so I wanted to propose to him there," Phelps told ABC News. "When I got invited to the holiday tour - six months to the day that we had been there on our first date - it was way too much of a coincidence to pass up."

The moment, which Phelps described as a complete surprise to Schock, was captured on camera by fellow tour-goers. Some of the images have since gone viral online.

The White House declined to comment on the engagement. No word on whether the Obamas knew what happened in their halls.

Phelps said his public engagement - made possible in part because of the repeal of "Don't Ask, Don't Tell" - has been well-received among his Marine Corps peers. But he noted that there could be a rocky road ahead for their relationship after the nuptials planned for next spring.

"The one thing that is overshadowing things," he said, "is the fact that the Defense of Marriage Act is still in effect and the DOD [Defense Department] isn't going to recognize our marriage.

"I'm expecting to get orders to Japan next summer, but as of right now, because they're not going to recognize Ben as my spouse, they're not going to pay for him to accompany me; he's not going to have any health care coverage; and, he's not going to have access to the base while I'm gone," he said.

"I'd have to get permission to live out in town as a 'single officer,' so we'll have to figure that out," he said.

The Supreme Court will later this year review the constitutionality of the Defense of Marriage Act, which defines marriage for federal purposes as between one man and one woman.

(Credit: Jennifer Cintron/American Military Partner Association)