help with ptsd?

I'm in high school. last year, I was sexually harassed by a guy for about 3 months. he manipulated me in to not telling anyone, but eventually I was able to get away from him and tell the school counselors and vice principal. nothing was ever done about the guy, but they did tell him to stop touching me. recently, seeing him in school has been triggering panic attacks and I don't know what to do about it. tips?