Complex sentence: Shortly thereafter, Castle, his wife, Maria and their children were in New York's Central Park for an afternoon picnic when they witnessed a Mafia gangland execution; an informant had been hanged from a tree.
Split into simpler sentences: Shortly thereafter, Castle, his wife, Maria and their children were in New York's Central Park for an afternoon picnic when they witnessed a Mafia execution. A gangland execution; an informant had been hanged from a tree.