That happened to me, kinda. It was someone that I looked up to, and he, well, did something he really shouldn't have. But once I got to [pen tap] know him, I realized that he wasn't really evil, he just had some psychological issues involving his dad. I talked to him about it, and soon enough he was able to conquer his personal demons with my help.

So my advice? Confront him about it. Most people don't do bad things without a reason, you know?