President Obama and First Lady Michelle Obama surprised a Northeastern University a cappella group this week when the two unexpectedly showed up to a White House holiday party to watch the students sing.

All 15 members of The Nor’easters traveled to 1600 Pennsylvania Ave. to perform for guests at a holiday party, but the group was never told, nor did any of them expect, to sing for the Obamas.

“We were all in shock,” Jessie Litwin, the a cappella group’s business manager, said, according to a press release from the university.

The group had been asked to prepare a special 60-second performance in addition to their main 20-minute set, which included holiday songs and a few contemporary pieces, the release said.

David Corzier, a senior and president of the group, had figured White House officials requested the shorter performance so they could film it for future use.

When the group finished their main set, they were told the Obamas would be stopping by to watch the next performance.