Today in Union Square, people are gathering to celebrate MCA Day, which will honor the late Adam "MCA" Yauch of the Beastie Boys. It seems that bandmate Adam "Ad-Rock" Horovitz was moved by the public outpouring—enough so that he is participating in the event as well!

You can see more photos of Ad-Rock talking to fans at the low-key event here, here and here. As organizer Michael Kearney told us, there is no overarching structure to the event, but he hopes that all the "fans, dancers, DJ's, MC's, artists, grandparents, cab drivers, suits and astronauts" would come out and "share a memory, spin a track, bust a move, show a tattoo, shake a hand, spread a message."

The event is going on all day, and Kearny encourages people to bring songs, memories, and anything else that will help pay tribute to Yauch and his life. You can also be like the man in the photo below, and contribute artistically: