Jay Bryant, 52, pleaded guilty Monday to murder in the 1997 killing of Jam Master Jay, the pioneering Run-DMC deejay and rapper. Bryant admitted he helped others gain entry to a building to ambush the victim. The case went unsolved for two decades before charges were filed. Jam Master Jay, born Jason Mizell, was shot and killed in his Queens recording studio on October 30, 1997. He was 37. Run-DMC became one of hip-hop's most influential groups, helping bring the genre into the mainstream in the 1980s. Jam Master Jay's role as deejay and producer was central to the group's sound and success. The long delay in solving the case reflected difficulties investigators faced in securing witness cooperation and building evidence. Bryant's guilty plea resolves one of hip-hop's most prominent unsolved murders and brings closure to the artist's family and fans nearly a quarter-century after his death.