A Bad Start

I was sitting on my porch tutoring a student when I learned that my new next door neighbor might be a chronic source of sexual harassment for his female students. He's an English professor in a nearby town, and he's lived here maybe a month or two. It was evening, and he wasn't there, but into our concession walked a 16- or 17-year-old girl, dressed up and looking guilty. She went to his door, knocked, then tried to just walk in, which is weirdly familiar for a student -- my students curtsy and bow when they show up at my door, and I'm not even as intimidating as a normal Beninese professor.
Anyway, she knocked, he wasn't there, she left. Twenty minutes later he drove in, and within 30 seconds she walked back in, meaning that she'd been sitting just outside the concession, in the dark alone, for all that time. They talked in lowered voices, I openly glared at them for the duration of the conversation, and she left again...only to return a minute later and walk right into his house. She closed the door behind her.
I was SO uncomfortable. I asked the student I was teaching what was happening, and she laughed at my naiveté and gave me a very clear look.
"He does this all the time. I asked a girl from his school, and she said he's not good. Girls go over to his house a lot. Did you hear his last phone conversation? It was a girl wanting to know if he would change her grade from a zero."
I almost cried right then, and the rest of our tutoring session was essentially worthless. Somehow, I guess I convinced myself that if I worked from the girl's end on sexual harrassment and didn't ask specific questions of professors who I know would name names, I wouldn't have to see it happen in person. Stupid, I know, but i made it 22 months without it being blatantly visible, and I thought I just might make it.
I didn't. I walked by a few times and looked in the window, and each time they were just sitting at the table talking. She left an hour later, and I guess I have no evidence that I should be uncomfortable... Except I am. It is not normal for a single male teacher to have a female student over to his house alone, and definitely not normal to close the door.
After she left, I confronted him-- I had to. I think I would have lost respect in myself if I hadn't. I was polite (somehow) and not too confrontational (I spoke in English so that our neighbors wouldn't hear) but I made it clear that I saw his visitor and that I wasn't okay with him having female student visitors. At all. He assured me that he was just discussing a private family matter with her, that I could always look in and see them at the table, and that a student would never go back into his bedroom. I suggested that he meet his students on his porch, outside, so that it'd be clear that he wasn't doing anything immoral. I thanked him, told him I thought I could trust him, and said goodnight.
I don't totally trust him, especially because of his reputation, but I am pretty sure that nothing happened last night. He knows now, though, that I am watching, and that I'm aware of what might be happening... Maybe that'll be enough to make him think twice. I hope it is.