Complex sentence: It was the fourth-deadliest nightclub fire in U.S. history, killing 100 people, and the second deadliest in New England, surpassed by the Cocoanut Grove fire which resulted in 492 deaths.
Split into simpler sentences: It was the fourth-deadliest nightclub fire in U.S. history, killing 100 people. It stands as the fourth deadliest nightclub fire in America and the second deadliest in New England, surpassed by the Cocoanut Grove fire which resulted in 492 deaths.