This has nothing to do with HR. This was a criminal matter, and he could have called the police at any time.
I suspect Joe wasn’t equipped to understand what was going on. But that doesn’t mean he doesn’t bear any reponsibility for what happened.
I tend to blame the athletic department. This was the cew that ran women’s basketball coach Rene Portland out of town after some accusations from a disgruntled lesbian basketball player. They were plenty pro-active when they wanted to be.