Being disrespectful in a public place (and we don't know if they were disrespectful. What is too loud? Who determines that?) warrants a death penalty by a random citizen? That's crazy. When I see something outside that looks questionable, I call the police. They can determine what is allowed or not. Who is he to be judge and jury? It sounds to me that Mr. Dunn was the one with little respect for his fellow man.
Possiblely everyone involved!