They are laughing with him. Because it’s not his joke; it’s their joke.
The cop raised his head to the buzzard-lined roofline of the Municipal Building and began to laugh. They cried harsh cawing sounds back down at him, and Johnny was not able to stifle the thought which came to him then. It was horrible because it was so convincing.
They are laughing with him. Because it’s not his joke; it’s their joke.

