The day after Facebook founder Mark Zuckerberg officially became a multi-billionaire via the most anticipated IPO ever, he wed his girlfriend of more than nine years. In a private ceremony in Palo Alto, California, Zuckerberg married his college sweetheart Priscilla Chan. Chan, who graduated medical school last week at University of California at San Francisco, has dated Zuckerberg since his dorm room days prior to the launching of Facebook.

The guests all thought they were coming to celebrate Chan’s graduation but were told after they arrived that the event was in fact a wedding. “Everybody was shocked,” one guest told the AP. Zuckerberg made the nuptials public when he updated his status to “married,” which garnered 800,000 likes by Sunday evening.

According to the Mercury News, a special performer was brought in to entertain the guests; Green Day’s Billie Joe Armstrong sang a few acoustic tunes including “Tell Me When It’s Time To Say I Love You.” In a TMZ video, with audio slightly obscured by passing cars, Billie can be heard dedicating a song to the newlyweds. “This song is one I wrote for my wife of 18 years… uh… it better be for her or I’d be in trouble. This song’s called ‘Last Night On Earth.’”

Green Day is currently in studio recording a trilogy titled ¡Uno! ¡Dos! ¡Tré! with the first album due in September.

No word yet if Billie Joe was a guest or a paid performer. Calls to Green Day’s publicists were not immediately returned.

-Jay Tilles, CBS Local