Complex sentence: Later, Soule testified against Chivington during the inquiry into the Sand Creek Massacre, and was assassinated in Denver soon afterward; his murder was believed to have been an act of revenge by Chivington loyalists for Soule's testimony.
Split into simpler sentences: Later, Soule testified against Chivington during the inquiry into the Sand Creek Massacre, and was assassinated in Denver soon afterward. His murder was believed to have been an act of revenge by Chivington loyalists for Soule's testimony.