An inmate in his early 20s died at the South Bay House of Correction in Boston on Sunday, authorities said. Peter Van Delft, a spokesman for the Suffolk County sheriff’s office, said the death “appears to have been inmate-on-inmate violence.” The man’s name was not immediately available, said Jake Wark, a spokesman for the Suffolk County district attorney’s office. James Kenneally, a spokesman for the Police Department, said the inmate was a man in his early 20s. The district attorney’s office and Boston Police are investigating, Wark said. No charges have been sought.