Reputed drug lord Howard (Pappy) Mason was indicted on federal racketeering charges in the 1988 execution-style slaying of rookie Officer Edward Byrne, authorities said. Mason, who is in state prison, was charged with masterminding the killing of Byrne, 22, who was shot five times in the head while guarding the home of a witness in a drug case. Byrne was killed Feb. 26, 1988, the day after Mason was arrested on gun possession charges. Four young men--all admitted crack dealers--were convicted of the slaying, which prosecutors believe was ordered by Mason in retaliation for his imprisonment. The four are serving state prison terms of 25 years to life.