Baby Left in Car Social Experiment

In this social experiment an actor playing the mother leaves her child in the car while shopping. They park the car on a public street in view of passersby.

When the researchers notice that people do not stop they play audio of a babys cries to try to get peoples attention. No one has stopped even though it is a hot day. Even when people hear the cries no one stops to help; a woman with her son finally stops and calls the police to report that the child had been left. The woman then confronts the actor.

Another man calls the police and tells the actor you should be shot. Are some of the passersby experiencing negative state relief hypothesis? Why or why not? How are peoples reactions different when in groups?