"They were all about partying. They were downing one Bitter Cherry Salome Sour after another, until they moved on to super strong Belvedere vodka and sodas," Contactmusic quoted a source as telling FOX411. "They looked like they were really celebrating!" the source added. The 21-year-old star and his pals insisted on toasting each other whenever one of them went to the bar and came back with another drink.