Best Friend leaves school because of teasing. My fault?? Pleasee help!?

One of my best boy friends [[no relationship, he was just a friend]] left my school because he got teased 24/7. He I guess was an easy target because he was the sorta popular type. I joked/ flirted with him sometimes. I feel like I was part of the reason he left. I asked him if I was, but he said I wasn't, it was a girl named Erika's fault. I think he was just saying that to not make me feel bad, but I feel 100% guilty.