BEAUMONT, Texas—Seven inmates have been charged with killing two fellow prisoners and wounding two others during a January attack at a federal prison in Texas that led to a nationwide lockdown of the federal prison system. The 15-count indictment filed this week includes charges of racketeering, murder, and attempted murder against Juan Carolos Rivas-Moreiera; Dimas Alfaro-Granados; Raul Landaverde-Giron; Larry Navarete; Jorge Parada; Hector Ramires; and Sergio Sibrian. The seven remain in federal custody and court documents do not list attorneys who could speak on their behalf. The Jan. 31 attack was inside USP Beaumont in Beaumont, Texas. Prosecutors say the seven are members of the violent MS-13 gang and attacked rival gang members of the Mexican Mafia and its affiliate, the Sureños. “Deterring prison violence remains a priority for the Department,” U.S. Attorney Brit Featherston of the Eastern District of Texas said in a statement Thursday. “Any prisoner who causes …