Kevin needs to leave for work but finds out that his driveway is blocked by another car. He gets into an argument with John - the driver of the other car. Kevin pushes John and John punches Kevin in the face. At that point, they are separated by a third person. A few moments later, Kevin suddenly falls unconscious and dies by the time the police arrive. An autopsy shows that Kevin had major heart disease, but the stressors from the argument and the punch caused a fatal bout of arrhythmia resulting in sudden cardiac arrest.

What is the cause of Kevin's death? Should John be held responsible for Kevin's death or not? Please explain.