"Pulling someone down will never help you reach the top."
If i was a part of this group of friends i would immediately go delete the blog. I would also stop socializing with them because they are horrible people. Then I would go find Chris and get him some help to prevent anymore mental pain. If I was in Chris's position I would feel terrible almost as much to not come to school or out in public. Most likely the bullying would still not stop so i would tell my parents and teachers. The people responsible deserve to be punished.
If you notice the bullying and do nothing about it this shows the bully that there are no consequences and he can keep doing it. Some things you can do to act against bullying is tell an adult and get the victim help. Standing up for the person bullied makes your school a better place and improves students experience. It shows the bullies there will be consequences for their actions and they cant just get away with it.