Fitzgerald provides numerous examples of foreshadowing in Chapter 8 which make it obvious to the reader that George Wilson is going to kill Gatsby.
1. After Myrtle's death, George's frame of mind deteriorates rapidly, and his illogical behavior hints that he is unable to control himself. He is unresponsive to many of Michaelis's questions. He mutters incoherently. He dwells on the events surrounding his wife's death and has a "bewildered look" in his eyes.
2. He blames Myrtle's death on her lover because he believes that her lover was driving the car that struck her. He shows Michaelis the dog leash and then says that "he murdered her" (166). George then mentions that he has a way of finding out who the man driving the car is and will not be swayed from his desire to find the man.
3. Finally, after George sets out on his quest to find the man, Fitzgerald writes that he went from garage to garage until he had found out Gatsby's name.