bad behavoir in library books

Lately Erik has observed some bad behavior in library books. He has a guidebook out, Sierra Nevada Natural History, and someone cut out one of the pictures in the moth/butterfly section--it was done expertly, as if with an exacto knife. This was premeditated! Then today he has an art book out, a book of Rubens, and someone's cut out whole pages from it. What kind of person would be so selfish?