Digital Milenium Copyright Act?

[Ni Ckel]

I have a legal question. My friend recently started getting threatening messages from an anonymous cyber-bully about stolen photographs. My friend goes to conventions in the area, takes pictures for money, then sells those pictures back to the person who paid.
He begin to get messages about two weeks ago saying he stole photos from another con photographer, then fraudulently sold them. This morning he got a message from DMCA saying they confiscated his photos because of illegal practices. Here is the exact message sent to me by him:
"Someone who demanded we take down photos of them and copies as their profile photo... without informing us, with the watermark edited out... and without permission or a link back. DMCA take down notice sent."
I'm wondering if we have a legal matter on our hands. If this is something i can sue for, because of no evidence, it would really help me out. I don't understand the Act very well, but i did read up on it a bit on Wikipedia, with not so much help. If someone could help us out here with knowledge of this Act or similar cases, it would be much appreciated!