Answer:
Wes made this decision because he wanted to send a message to the people who underestimate him, showing that they shouldn't mess with him if they don't want to suffer. He also does it as a revenge for the step that Ray gave him.
Step-by-step explanation:
Ray hit Wes and it left him looking weak and helpless in society. He couldn't allow that kind of reputation to follow him, besides, he knew he had to get back at Ray for giving him a beating. For this reason, he decided to shoot Ray, who besides promoting strong revenge showed to society that he should be feared and respected and not underestimated.