LOS ANGELES (Reuters) - The Las Vegas deputy district attorney who prosecuted Paris Hilton for cocaine possession was arrested over the weekend after allegedly buying a rock of cocaine, authorities said on Monday. Clark County Deputy District Attorney David Schubert, 47, was taken into custody in Las Vegas on Saturday afternoon and booked on one count of cocaine possession. Schubert, who has prosecuted Hilton and pop star Bruno Mars on similar charges, was released on Sunday after posting bail and was scheduled for an initial court appearance on Monday. Im very disappointed to learn one of our prosecutors was allegedly buying rock cocaine, Clark County District Attorney David Roger told Reuters in a telephone interview.