Where’s the line between minding your own business and speaking up?

I used to know a guy who is in his 40s when I was in highschool. He seemed really cool at first, but some shady stuff went down with my friend and him. Everyone involved seemed to have the same story, except for him. (I wasn’t involved, but he saw me at my job and confided to me. I assumed what he was saying was true, based on my friends past. But then when around my friends family, they brought up the situation and it was completely different than what he had told me. )

And after that, he had tried getting me to smoke with him and stuff, but I had a bad feeling in my gut about it. I ended up passing. I didn’t even feel comfortable smoking anything he gave me bc I was afraid it could be laced.

The more I’ve heard about him throughout the years, the same story has come up multiple times.

It seems like he goes after girls who are 18-25, they start doing drugs, and they end up stuck with him for a while because they end up depending on him to care for them. Then when somehow they end up leaving him, he claims he broke it off because they got into drugs and started sleeping with the drug dealers. most of these women have said that they never cheated on him and that he’s the one that had introduced them to the drugs/dealers. He does not seem to do drugs at all, besides weed.

I can’t 100% say what is exactly going on with that situation, but there definitely seems to be a pattern going on.

I recently started noticing that he’s been commenting things on a girl who I’ve met before, but I know necessarily know well. I feel like I want to suggest she try and be careful around him, but They could be family for all I know. I don’t want to start anything. But I’m also worried for her.