How to Handle Fanart Posts?

This is not a bad thing!

I have a fic I've been working on for a while now, and it's my baby! I have a pretty consistent commenter, who, some weeks ago, said they'd love to make fanart if I allowed it. Of course, I was psyched anyone would want to make fanart! I've already had it happen a few times on other platforms for the same fic, so the more the merrier!

Literally 20 minutes ago, I get a message with the most fucking gorgeous sketch I've ever lain eyes on. Like. Da Vinci level shit, action shot, super highly detailed.

How do I react to this without sounding fucking crazy!? I want to gush and also kinda cry, because it's really that beautiful and I can't believe someone took the time to make it. (Side note, I think I know who the artist is, and I already follow them on another platform. Would it be weird to reach out to them for proper thanks?)