Complex sentence: In September 1845, a mob of anti-Mormon arsonists targeted Morley's Settlement and burned down the Durfee home and then burned down the homes of dozens of other Mormon families.
Split into simpler sentences: In September 1845, a mob of anti-Mormon arsonists rushed upon Morley's Settlement. They burned down the Durfee home and, shortly thereafter, burned down the homes of dozens of other Mormon families.