Antonio "Mack" Hall, a 30-year-old Baltimorean, was indicted Dec. 2 by a federal grand jury for murdering a federal witness, Kareem Kelly Guest, in Westport in 2009, according to a press release issued today by the U.S. Attorney's Office in Maryland. Guest's cooperation with a law enforcers' investigation of a violent drug conspiracy in the Westport neighborhood of South Baltimore was documented in an FBI report that, through a criminal-defense attorney's failure to comply with an agreement with prosecutors to keep the document under wraps, became widely distributed in the neighborhood. The indictment against Hall is spare on details, saying only that he killed Guest and, while having a felony record, illegally possessed "two rounds of CCI 9mm Luger ammunition"—presumably the bullets that killed Guest. But the cause of Guest's fate, and the dissemination of information about his cooperation with law enforcement, has been covered extensively in City Paper. The suspicion that Guest had been killed in retaliation for cooperating first came to light publicly in May, when Raine Zircon Curtis was charged with obstructing justice and lying to federal agents and the grand jury. More details emerged during Curtis' subsequent detention hearing. The press release of Hall's indictment says the investigation of Guest's murder is ongoing. "This case tragically highlights the risks that arise when sensitive information about witnesses in criminal cases is not protected," U.S. Attorney Rod J. Rosenstein said in the press release.  "Solving Kareem Guest's murder has been at the top of our list since the day he was killed.  This prosecution demonstrates our commitment to use every resource at our disposal to pursue criminals who attack or intimidate witnesses." Prosecutors may seek the death penalty against Hall, a decision, the press release states, that rests with the U.S. Attorney General "after carefully considering the defendant's background and the circumstances of the crime." Online court records indicate that Hall was last convicted of a crime in June 2009, about three months before Guest's killing; he was sentenced to two days of incarceration for drug possession. Before that, he received a one-day sentence for attempted drug dealing in 2007—which brought on a probation violation that netted a six-month sentence in a 2004 drug-dealing case for which he'd received seven years, nearly all of it suspended. Over the years Hall has beaten numerous other state charges in Baltimore City Circuit Court, including for attempted murder, assault, illegal weapons, and drug-related crimes.