Complex sentence: Bell died in Greenville in 1960,1965 or 1966, possibly during a civil rights march, although other sources suggest death by natural causes, murder due to his involvement in the civil rights movement, and black magic.
Split into simpler sentences: Bell died in Greenville in 1960,1965 or 1966. One source states that he died during a civil rights march; other sources suggest that his death was due to natural causes, murder on account of his involvement in the civil rights movement, or black magic.