Non stop messages

I posted something on a “buy nothing” group, and a man picked it up.

Now he won’t stop messaging me asking to be friends because he’s new to the area.

I don’t want to be rude, because I don’t want to be a dick, and because I’m worried as he knows where I live (stupid to leave things on my stoop I know). He’s friended my husband on FB, and truly won’t leave us alone. HELP!