Why do people do this alot. what does it mean also.?

like whenever someone is in trouble or getting yelled at by or teacher or your folks why do the guys who watch it like smile at each other or laugh to themselves? what are they trying to say. give you a example. my neighbors the peterson boys said to me hey come on there a wildfire lets go check it out I was walking with them and my mom was with me. she let me go with them for a while then she scolded me for something like since i was with my dog walking him. the two peterson boys then smiled and laughed at each other after that happened to me.