Complex sentence: He left the band to pursue a career in law enforcement, on December 11,2007 he rejoined Iced Earth replacing Tim'Ripper' Owens, who had replaced him a few years earlier.
Split into simpler sentences: He left the band to pursue a career in law enforcement. Then on December 11,2007 he rejoined Iced Earth replacing Tim'Ripper' Owens, who had replaced him a few years earlier.