Hip-hop lost one of its greats in the Beastie Boys' Adam Yauch, better known as MCA. Yauch passed away at the age of 47 today, May 4, following a long battle with cancer, leaving the world both shocked and saddened. Fans of all genres were devastated by the news -- and many took to Twitter to mourn the loss of the Brooklyn legend. Some used lyrics, some used memories, but all were universally heartbroken. #RIPMCA.